Is PVC an acceptable vent material for flue gases?

Tim McElwain

An excellent article on this subject by Ron George in the May 2011 Plumbing Engineer Magazine. He supports with his findings many of the things i have posted here. Read the article if you can it will open your eyes to this dangerous practice.



Ron is President of Plumb-Tech Design and Consulting Services LLC. He has served as chairman of the International Residential Plumbing and Mechanical Code Committee. Visit <a href="http://www.plumb-techllc.com">www.plumb-techllc.com</a> his e-,mail is <a href="mailto:ron@plumb-techllc.com">ron@plumb-techllc.com</a> or phone 734-755-1908.

Tim McElwain

Here is the article, I hope it fits?

Is PVC an acceptable vent material for flue gases?



By Ron George,CPD,

President, Ron George Design & Consulting Svcs.





I recently inspected the mechanical systems in student housing at a Midwest university. The school had hundreds of apartments in numerous buildings with high efficiency water heaters that were installed more than 10 years ago. There were reported problems of not having enough hot water. I recently inspected the mechanical systems in student housing at a Midwest university. The school had hundreds of apartments in numerous buildings with high efficiency water heaters that were installed more than 10 years ago. There were reported problems of not having enough hot water.





My inspection revealed a high efficiency water heater with purple/brownish PVC pipes and yellowish PVC flue pipe fittings. The flue pipes were obviously deformed from heat, and they were sagging. A maintenance man for the university said that some really bad pipes had come apart at the fittings and melted. This set off the carbon monoxide alarm and prompted a maintenance call. The water heater had scaled up due to minerals in the water supply; this caused the flue gas temperatures to rise, which created the noted problems.





The pipe was Schedule 40 PVC pipe. Although the water heater installation manual we obtained recommended using PVC pipe as a flue material, PVC pipe manufacturers do not recommend this. I called the manufacturer of the PVC pipe in this case and asked the representative a few questions about using PVC pipe as a combustion flue for fuel gases. He was quite familiar with this issue and emailed me a link to the company’s technical manual, which discussed all of the physical and temperature limitations of the piping.



He said that the company has had numerous complaints about PVC pipes used for venting flue gases, and that they always point out that they do not recommend this usage and that there is no listing for it in their manual. He has asked every major manufacturer of boilers and water heaters for data to support the recommendations in their literature for the use of PVC pipe for combustion flue materials but has not received any replies.





This is concerning to me. Just because a manufacturer recommends using PVC does not mean that it is acceptable or safe. Just because PVC works in new installations does not mean that a condition cannot occur in which scale builds up over a short time in hard water areas and causes high flue gas temperatures. Most boiler and water heater manufacturers list other ways of venting with stainless steel, but they seem to always recommend the cheapest way in their literature, in an attempt to make the boiler seem more affordable to consumers.





The piping manufacturer’s PVC pipe technical manual has the following information:





Using Plastics for Combustion Gas Venting





The piping manufacturer recommends that inquiries about the suitability of plastic piping systems for venting combustion gases should be directed to the manufacturer of the water or space heating equipment being installed.





As stated in the International Code Council’s International Fuel Gas Code 503.4.1.1:

Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer’s installation instructions.





Furthermore, several of the ASTM standards applicable to PVC plastic pipe and fittings that this company manufactures their pipe to include the following note: This standard specification for PVC pipe does not include requirements for pipe and fittings intended to be used to vent combustion gases.





There is no standard referenced in any of the codes in the United States for a plastic flue vent for combustion flue gas piping, although many water heater and boiler manufacturers recommend this. There is a Canadian standard, ULC S636, but that standard has several flaws in that it allows flue gas temperatures that exceed the temperature limits of the pipe material manufacturers.





The maximum temperatures listed in the ABS, PVC and CPVC pipe manufacturers’ technical literature are shown in the following table. Any temperatures above the rated temperature will allow the pipe to melt, sag and, possibly, collapse or pull apart. There are serious consequences with carbon monoxide asphyxiation and fire that cannot be ignored.





Generally, for a new condensing water heater or boiler, the stack temperature will be about 20 degrees higher than the water temperature. The design and efficiency of the unit, along with several other factors, including water quality, will affect the stack temperature. If a water heater is set to store water at 140 F to minimize Legionella bacteria growth, the flue gas temperature will be about 160 F when the heater is new.







As scale builds up and the heater efficiency falls off, the flue gas temperatures can easily increase to over 350 degrees F. Even if someone had their water heater set at 120 F, with scaling, the flue gas temperatures can rise well above 300 F. Boiler thermostats or burner controls are generally limited to 200 F, commercial water heater thermostats or burner controls to 180 F and residential water heater burner controls to 160 F, and all can overshoot by several degrees. As scale builds up on the heating surfaces, the scale insulates the flue gases from the hot water in the system, causing the flue gas temperatures to increase.





As scale builds up and the heater efficiency falls off, the flue gas temperatures can easily increase to over 350 degrees F. Even if someone had their water heater set at 120 F, with scaling, the flue gas temperatures can rise well above 300 F. Boiler thermostats or burner controls are generally limited to 200 F, commercial water heater thermostats or burner controls to 180 F and residential water heater burner controls to 160 F, and all can overshoot by several degrees. As scale builds up on the heating surfaces, the scale insulates the flue gases from the hot water in the system, causing the flue gas temperatures to increase.





Some boiler and water heater manufacturers offer stack or flue gas temperature gauges as a way to see whether the unit is scaling up and losing efficiency, which is helpful for monitoring the flue condition. A temperature sensor or probe with a high-limit control could be inserted into the flue at the flue connection to the boiler or water heater.





This control would shut off the burner if the flue gas temperature exceeds the temperature rating of the flue pipe.



A standard will be needed for plastic flue pipes that should include a temperature gauge and a high limit probe. Then PVC, CPVC and polypropylene flue gas piping can be safely used on high efficiency boilers and water heaters. This would be an answer to the dilemma of cost versus safety.





Without a standard for proper use of these safety devices in combination with plastic flue gas piping or without the use of stainless steel flues, plastic flue materials can melt as flue gas temperatures rise. Not only is energy lost when this happens but flues can become blocked or disconnected, which can be a carbon monoxide or a fire danger.





A family of four died in Aspen, Colorado, in 2008, of carbon monoxide poisoning from the failure of PVC plastic flue pipes on a condensing snow melting boiler system in a rental property. The plastic pipe manufacturer was not at fault, because they had published limitations on the use of their piping, and they had not recommended PVC piping for that application. The boiler manufacturer that recommended using PVC pipe as flue material was a target of the liability claim by surviving family members.





I have heard arguments by many contractors that do not believe PVC flue venting for combustion gases is a problem, but I have seen melted and discolored piping in many of my investigations, so I know it is a problem. I also see the proliferation of recommendations from high efficiency, condensing boiler and water heater equipment manufacturers for the use of combustible and unlisted PVC piping products as corrosion resistant combustion flue venting.



This approach seems to be a way to lessen the initial cost of installing a high efficiency boiler or water heater. High efficiency equipment will cost significantly more than less efficient models, so there seems to be a movement by manufacturers to promote these unlisted and, therefore, non-code-approved materials over code approved and listed stainless steel flues, which are corrosion resistant.



This approach seems to be a way to lessen the initial cost of installing a high efficiency boiler or water heater. High efficiency equipment will cost significantly more than less efficient models, so there seems to be a movement by manufacturers to promote these unlisted and, therefore, non-code-approved materials over code approved and listed stainless steel flues, which are corrosion resistant.



Some people argue that the mechanical code allows you to follow the manufacturer’s recommendations. The 2009 International Mechanical Code (IMC) has the following language:





801.20 Plastic Vent Joints. Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer’s installation instructions.





Section 802 Vents





802.1 General. All vent systems shall be listed and labeled.





There is no listing for plastic piping for flue gas venting applications.





The 2009 IMC also has the following language:





Section 304 Installation





304.2 Conflicts. Where conflicts between this code and the conditions of listing or the manufacturer’s installation instructions occur, the provisions of this code shall apply.





Exception: Where a code provision is less restrictive than the conditions of the listing of the equipment or appliance or the manufacturer’s installation instructions, the conditions of the listing and the manufacturer’s installation instructions shall apply.





There is a conflict between sections 801.20 and 802.1. The water heater manufacturer’s installation instructions conflict with the requirement in section 802.1 that requires all vent systems to be listed and labeled for the application. PVC pipe is not listed and labeled as a combustion flue pipe material, as noted in the piping manufacturer’s notes above, yet manufacturers of the water heaters and boilers seem to be avoiding the issue, and they continue to recommend the use of PVC flue venting in their installation instructions.

 



Section 304.2 addresses conflicts. The code restriction requiring all flue materials to be listed and labeled for their intended purpose is more stringent language, so the more restrictive code requirement requiring listed and labeled flue pipe materials would apply. There is additional language in the International Fuel Gas Code.





I have not seen any testing data or an independent test report from a boiler or water heater manufacturer that shows that PVC piping has been tested and approved for the conditions it will likely see in a water heating or boiler installation. Any testing should include the extreme conditions when scaling occurs and flue gas temps rise, near the end of the equipment’s service life.





The Canadian standard, ULC S636, covers the design, construction and performance of gas venting systems intended for negative or positive pressure venting of gas-fired appliances producing flue gases having temperatures under the following:





1. Class I venting systems are suitable for gas-fired appliances producing flue gas temperatures of more than 135 C (275 F) but not more than 245 C (473 F);





2. Class II venting systems are suitable for gas-fired appliances producing flue gas temperatures of 135 C (275 F) or less;

 



3. Class II venting systems are further classified into four temperature ratings as follows:

(A) Up to and including 65 C (149 F)





This temperature limit was intended to allow the use of PVC pipe for use as a flue gas material. The temperature limit for PVC pipe is 140 F, and the allowable temperature in the ULC S636 standard exceeds the temperature limits set by PVC pipe manufacturers.





(B) Up to and including 90 C (190 F)





This temperature limit was intended to allow the use of CPVC pipe for use as a flue gas material. The temperature in the pipe manufacturer technical data is 180 F. The ULC S636 standard allows the material to exceed the limit for CPVC piping by 10 degrees Fahrenheit.





(C) Up to and including 110 C (230 F)





This temperature limit was intended to allow the use of Polypropylene (PP) pipe for use as a flue gas material. There is currently one manufacturer listed to this standard, but the potential for the flue gases to exceed the 230 F is still there. A high-limit switch to shut off the boiler or water heater would be advisable.





(D) Up to and including 135 C (275 F)





I am not aware of any plastic pipe manufacturers that meet this sub-section of the standard. The potential for the flue gas temperatures to exceed the 230 F is still there. A high-limit switch to shut off the boiler or water heater would be advisable.





It will be interesting to see which way the industry goes on this issue. There are forces pulling each way, and I believe that a significant change will be coming within the next few years. I hope the industry can develop a standard to allow low cost, high temperature plastic materials. I believe that we will see a few code changes on this topic in the next round of code hearings. The 2012 Code is nearing completion and should be available in 2011. The 2015 code cycle will begin in the not too distant future.



Ron George is president of Plumb-Tech Design & Consulting Services. He has served as Chairman of the International Residential Plumbing & Mechanical Code Committee. To contact Ron, write him at rgdc@rongeorgedesign.com.

 

Jean-David Beyer

Metered my PVC vent pipe today.

I am not a professional, but I am curious about these things.



Today I had just run my dishwasher and took my portable IR meter to see what my white 3" PVC exhaust vent pipe measured.



The boiler (W-M Ultra 3) was trying to produce 170F water to send to my indirect hot water heater. The water was a little over 70F when it started (warm out, and no heat was required for the house since midnight, if not before). The indirect's aquastat was set a little over 120F.



The vent comes out of the top of the boiler, goes up about 15", goes through a 45 degree elbow, a very short piece of straight pipe, then another 45 degree elbow, and straight up near the ceiling, where it goes through a 90 degree elbow and on its way.



As this pipe was warming up, I measured around to find the hottest spot. This proved to be at the end of the second 45 degree elbow, on the outside of the curve where the exhaust was probably hitting it.



I watched the IR thermometer and glanced at the supply and return temperatures going to and from the indirect. The supply never made it to 175F because the aquastat was satisfied at about 170F supply. The return was about 150F at that point. When that happened, the outside temperature of the PVC vent pipe was 111F. This experiment took between 5 and 10 minutes, but I did not time it.



Comments by experts welcomed.

CMadatMe

How Its Done

Here is the trick of the trade and how the mfgs get away with it. It's very simple and in every installation manual.



They list that PVC can be used if it meets ASTDM 1785. 1785 clearly states that PVC can be used in temps up to 140 degrees. But nobody reads the stupid manuals. They will also see the other means of venting Z-Vent or a vent pipe that meets ULCS-636. They have covered there butts and you the installer now holds the bag. Installing PVC as a vent material exceeds the standard so you are suppose to go the next recommended vent pipe in the manual!!!



Problem is most contractors couldn't tell you what ASTDM 1785 even says. They just assume the pipe can be used because it is in the manual.

Mark Eatherton

I hate to say it, but....

I've been using PVC for venting the high efficiency appliances for as long as they have been on this side of the pond. I regularly go by the first Munchkin job I did and observe and sample the PVC serving this neglected, high temperature (strictly DHW thru a HTP tank) application and other than exterior surface yellowing, I've not seen any degradation that would cause me concern.



I also do work with a forensic engineering firm with 10 employees, and they are specialist in CO and fire, explosion and collapse, and I've asked them many times if they've ever seen a failure of PVC venting systems, and the answer is one (1) in all the hundreds of investigations they have performed, and that was on an appliance that was being run on LP without a conversion kit. He said it basically melted the first few inches of venting, and collapsed inside of the no hub connector.



Now, with all due respect to Mr George, he sites the Aspen case. I am under the impression that the PVC joint was not glued, and came apart. Will using S.S. guarantee proper installation and fastening? I don't think so. Nothing will keep people form doing stupid things. No approved materials, no approved methods.



With that said, how many Wallies have witnessed deformed or failed PVC piping on gas fired appliances?



I'm just guessing here, but if it is proven that PVC does have the ability to withstand the operating temperatures/pressures in these new systems, the PVC manufacturers will line up and get their certifications, and start charging a premium for their product....



As for high temperature flue gasses, the Knight has a sensor that limits the fire. If (and you know they are out there) someone neglects their appliance, and abuses it, the flue gas sensor will limit the burner, and the consumer will eventually complain about DHW or SH shortages.



Just saying... Show me the evidence of failures, all standards set aside, for the time being, and I will join your band.



ME

TonyS

I have replaced some

of the first condensing furnaces that I installed because of failed exchangers after 20 years. The PVC outlasted the exchanger, so you might as well consider the steel exchanger unfit to. I did not reuse the PVC but I could have.

Jean-David Beyer

PVC can be used in temps up to 140 degrees.

What I measured was the temperature at the outside of the PVC vent pipe. It seems to me that it would probably be better to measure the inside wall of the vent pipe, other than the technical difficulties of doing so.



Now, if I never have my boiler serviced, then the exhaust temperature wil lgo up as the crud builds up in the heat exchanger. I do get it serviced, so this should help.



My boiler has an exhaust temperature probe (actually two probes in one for redundancy). This dual sensor is in the vent pipe immediately as it comes out the bottom of the heat exchanger. Inside the boiler, the vent pipe seems to be stainless and it exits the top of the boiler, perhaps 2 feet up, where it changes over to PVC. So the exhaust as it hits the PVC is probably a little less than when it exits the boiler. If the two flue sensors are more than 10F apart, the boiler will shut down until the two sensors are within 10F. If the flue temperature exceeds 210F, it will shut down for 1.5 minutes if the temperature gets back down. If flue temperature gets up to 220F, it will shut down and will not restart until it is manually reset. This may prevent immediate problems, but it sure will not keep the PVC under 140F.



I see that vent pipe every day, so I would probably notice a color change, other than a very slight one. I wonder if a color change would be enough to determine when the pipe should be changed.

Jean-David Beyer

I am under the impression that the PVC joint was not glued

I know for sure that most of the joints in my vent system were not glued. One reason why I have a new contractor. The joints were purple, though, and that was enough to fool the inspector, unfortuanately. I doubt the contractor was trying to save money on glue,  but it certainly can happen.



It was like that for a year and a half, and I did not die, and my carbon monoxide detectors did not go off.



I wonder how lucky I was.



1.) The boiler, if properly adjusted, should put out only 60 ppm of carbon monoxide. I would not wish to breath that very long, but it would dilute fairly fast.



2.) The pressure inside the vent is not very high, though I have not measured it.



3.) If the vent did leak at the joints, the CO would leak into my garage, not directly into the house. The house is not perfectly sealed from the garage, but there is no door directly from the garage to the house.



4.) I have three carbon monoxide detectors; two of the standard big box store type and one in my bedroom that is the high sensitivity type.



5.) Of course, as soon as it was determined that the joints had not been glued, all that was replaced by my new contractor.

pipe4zen

temperature and pressure

is how they gey around it.



The PVC manufacturer is testing for a maximum temperature while at a given pressure.



A flue pipe is not under pressure, there is and open end to the outside(we hope). Pex is rated the same way also, the standard lists several max temp/pressure ratings.



One thing I do is size of pipe correctly, if a water heater is using 2" PVC but is vented long distances,including elbows, then an upsize should be done, so static pressure drop at the equipment is not high causing the high temps to linger around at the water heater.

Jean-David Beyer

vent pipe size

My boiler allows 2-inch or three-inch PVC for the distance and number of elbows in there. My installing contractor used 3-inch everywhere.



(Similarly with the copper and iron piping, where he used 1 1/4 inch where the manufacturer specified at least one-inch.)

TonyS

Tim

The article seems well written but fails to deliver some important information. High efficiency water heaters means nothing to most professionals. "Everything" today is high efficiency, so it has lost any real meaning. He should have at least broke it down into Condensing or Non-condensing and a little more info on the units would help.

Mark Eatherton

I agree with Tony....

Although Mr George is very well educated on what the code says, it would appear that he has little working knowledge of what is actually going on out in the field. I think most modcon manufacturers are well ahead of his thoughts as it pertains to protecting the flue gas disposal systems, and the possibility of a fouled heat exchanger...



Having not worked on every modcon that is out there, I can't vouch for all of them, but the experience I have with Lochinvar goes in a different direction than the statements in his article.



Now, if it were Plex Vent, I am certain that there would be a LOT more responses about seeing failures in the field. I know every one that I inspected was obviously cracking, crazing, checking and leaking. I've not seen any of that in the PVC venting systems I see on a regular basis.



I should probably ask the respondents to tell us whether it was a high efficiency modcon or just a forced draft water heater/furnace. Big difference in the operation of the two...



ME

hot_rod

If your PVC vent pipe

went from bright white to "brittle beige" in a couple years time I think you might wonder. This is one of many in a multi unit building. As I understand it the temperatures were cranked and the building was still under-heating.



So the concept of a high temperature flue gas condition, possibly scaled boiler which is not un-common in aluminum block boilers that may not have appropriate water or fluid quality. It could be a perfect storm brewing.



The product being used to vent by products of combustion should be listed to that purpose or we my be going down the same road, or rockier road than we did with the hight temperature plastic vent systems. Only that was designed for venting.



hr

Jean-David Beyer

Discolored PVC piping.

In that picture, both PVC pipes are discolored, although the exhaust one is more discolored than the air intake one.



How do you  account for the discoloring of the air intake pipe? Because it would be difficult for me to believe that the air intake was anywhere near 140F. And what is the cause of the lighter colored stripe a few inches below the red arrow?



Were these two pipes about to be replaced, or did you decide they were OK for continued service?

CMadatMe

Contractor Responsibility

In the end are we not talking about responsibility to educate your customer and allow them the choice of what vent material to use based on your recommendation.  Charlotte clearly states PVC is not rated above 140 degrees. The mfg installation manuals give you several ways to vent and reference standards. Is it again not the contractors responsibility to know what the standards mean.



If you were on the stand and I was the lawyer, the first question out of my mouth would be what does ASTM1785 mean? Next question, does the mfg of PVC state in it's techincal data that PVC is rated to 140 degree temperature? The third, did you check the standards of the other vent options as described in the mfg installation manul. The fourth, did you discuss each vent option with the plantiff and bring it to their attention that the heating appliance would be venting flue gases hotter then 140 degrees. The 5th, Why did you choose not to install the other venting products that were rated for flue gas temperatures the heating appliance would be producting?



Jury?

Jean-David Beyer

Educating the customer.

"In the end are we not talking about responsibility to educate your

customer and allow them the choice of what vent material to use based on

your recommendation."



Since I am a customer, not a contractor, I have an inclination to agree with you.



Had my contractor explained the difference, both technical, between CSST and black pipe for my gas, perhaps I would have selected black pipe even if it cost more. Similarly, had he discussed the difference between appropriate stainless venting and PVC, CPVC, polypropylen, or whatever, who knows what I would pick? But if I picked it, would the liability then fall on me? After all, he is the one with the license. If I insist he violate the code, and put it in writing, does that get him off the hook? IMAO, he should refuse and walk away.



But where do the lines get drawn? Should my contractor have told me about legionella and the cost of running my indirect 20F hotter and the cost of a suitable mixing valve as against the cost of hospital and medical bills? I suppose so. But at some point is it going too far? Should we discuss the relative merits of a Caleffi mixing valve vs one from Honeywell or Watts? At some point, pretty close to here, he will say I should do it myself. I do not want to be unreasonable about this.



I think I am atypical as a customer though. People I know could not care less about their heating systems. One did not even know where it was in her condo (a closet right off the living room). I wonder if she ever has it serviced? It is forced hot air, gas fired. Does she even change the air filters? Some buy a heating system like they buy a microwave oven: size, color, price. They do not want to know about, nor make, any of the decisions: that is what the contractor is for.



As I have said before: I am really glad I am not a contractor and have to deal with customers.

CMadatMe

In the Case

Of venting. Your telling them why your not using PVC and recommending one of the other vent methods that are availble to you.

Jean-David Beyer

In the Case Of venting

Of course, I happen to agree with you.



And incidentally, I think you have solved a problem in educating the consumer and having him make the decisions. You do not have the customer make the decision. You make it and explain why: because in your professional experience the alternatives are not safe enough to stake your reputation on them. Now if the customer insists on buying by price on a detail like that, then I hope you make enough on your business that you can afford to lose that customer.



If the customer has real money problems, you can discuss conventional boilers and mod-con boilers, pointing up the issue of up-front costs vs. continuing operating costs, and let the customer make that decision.



In my case, I would have gone for black iron gas pipe vs. CSST, for example, but I was not asked if I had a choice or not.



But so many of these should be really easy decisions. It looks to me that stainless vent pipe is about 10x more than PVC. Stated that way, it looks non-competitive, but when you figure it is only 4% of the cost of my boiler replacement (about the cost of the permits for the job), it is not unreasonable at all.

Tim McElwain

I have asked

Ron George to join the discussion here to defend his finding's and perhaps expand on some points made by those posting here.



I find this a critical concern for a number of reasons which I have expressed in the past including my findings of breakdown of chlorides and contaminating the combustion side of some of this high end equipment.



I hope he joins us and let us try to be civil in our discussion.

Jean-David Beyer

Than you.

I think that is a very good idea.



The main thing that comes to my mind is that he seems to be thinking about domestic hot water heaters, and not necessarily condensing boilers. There seem to be some condensing hot water heaters (if I am not mistaken), but I do not know their efficiency as shown by their exhaust gas temperatures.



It seems to me that with a condensing boiler, which would normally be run as a closed system, the chances of getting sediment on the water side of a heat exchanger would be fairly small. On the fire side, deposits should be easily detected and removed during annual mainitenance. I saw that done with mine, but it was only about a year old at the time, and it seemed pretty easy. If it were skipped for a few seasons, the stuff might be more difficult to remove. According to the regional rep from the boiler company, you should even be able to detect the need for cleaning by examining the exhaust gas temperature that can be obtained by diddling the buttons on the control panel. The exhaust temperature should be no more than 54F above the return water temperature. Of course different boilers would have different numbers. If I were putting 190F water into the indirect, that implies that it would be within spec. to get 244F exhaust temperature which would be a lot over the PVC pipe rating. I suppose the thing to do is keep an eye on the pipe and when it starts to turn yellow, to repalce it with AL29-4C. I suppose I can keep the PVC for the air supply.



I see no reason not to be polite. Rudeness makes it difficult for minds to meet., and in the last analysis, I assume we would all like as close to a definitive answer to this as we can get.

Charlie from wmass

I am simply sitting on the side line

with this discussion. I am just thinking of all the exhaust pipes that may need changed and who will the tab land with? If the use of PVC is determined to be dangerous on systems not running at proper radiant temperatures will the manufacturers of the boilers be held to task or will the home owner get the bill, or will it be a government funded issue with the scope of the problem? Granted if systems are running high temp the home owner would have been better off with a conventional cast iron boiler in my opinion.

Jean-David Beyer

As a homeowner who will probably get stuck with the tab,

I expect the government will not pay for any of it. There is probably no extremely large political party that represents homeowners of boilers with PVC venting systems to get the government to do anything. I know here in New Jersey we do have a state program to help homeowners remove in-ground oil storage tanks. My tank was removed in May 2009. The state has my grant application for the cost of remediation not covered by insurance. But just recently I was informed that the program is out of funds, and people are having to wait three years or more before there will be funding for it. I may have to wait less because my application was received long ago.



Judging by the Internet price of the amount of stainless needed to replace the exhaust of my system, it is about the same as the cost of the building permit I paid to have the boiler, hot water heater, and converting to two zones done. Around the cost of a 3-year service contract for my heating system. Of course, I would need to add labor, overhead, and profit to the cost of the stainless itself. I suppose I could do it myself, but I do not propose to do that.



Having measured the outside temperature of the PVC (111F) when making hot water for the indirect, and noticing no color change  of the exhaust pipe, it does not look like an emergency for me. Most of my house is radiant, where the return temperature is always less than 120F, and sometimes about 75F. The other heating zone is always less than 135F, and sometimes slightly less than 110F. The domestic hot water is the hottest, where the return temperatures can go up to 160F or so, for 5 or 10 minutes a few times a day (2 or 3, as far as I can tell).



I would like to find out if there is any need to replace the pipe before a color change. I would very much doubt I would be better off with a cast iron boiler, since the only high temperature use is for the indirect hot water heater that can get up to 175F supply temperature with about 155F return.

Jack

PVC for vent systems

Regardless of its performance over the years I think that as an unlisted product for the application, its days are numbered. Charlotte went thru some linguistic gymnastics a while back in the "Suitability of PVC for vent systems" letter. Essentially they acknowledge that it is not listed, say there isn't enough of an installed base to make a reasoned assessment of it suitability for venting (nonsnese) and then say it is up to the equip manuf to determine the best material for their system. This type thing is just blood in the water for the Trial Lawyers Assoc. This one will make polybutylene and Plexvent look minor. I hope I am wrong!



A part of this suitability discussion goes to the type of appliance. A warm air furnace that never gets its filter changed will run up on limit and cycle on and off on that limit. Once a boiler has heated and cooled its operating fluid becomes kind of an inert fluid and there is not much scaling...normally, that will take place. I have seen quite a bit of brown PVC on tank water heaters. I think this has been on mostly high duty cycle apps.



When Rinnai was designing their condensing water heaters we told them that for competitive purposes we needed a PVC vent system. Rinnai Japan Engineering took one look and said, No joy on PVC and we now have a Polyprop concentric vent. With their explanation, I have to agree with them. Every gallon of water going through a tankless water heater is fresh water. If, over time, the unit scales up you end up with an increased stack temp. A limit in the stack could be a solution, but it shows the product to be unreliable (hot/cold cycling shower) and I'm of the opinion that a limit is a safety control, not an operating control. Where PVC can take 156F the polyprop will take 250F. I'd rather take the high road on this with tankless and am pleased with the decision RJ engineering made.



I think a part of the problem PVC will have going forward is the availability of the Polyprop in the market. It is a better material and as the discussions heat up on PVC, and they are, the pressure will lead to the higher spec product...whether you need it or not.



Today, where is pvc NOT legal for use?

Jean-David Beyer

Today, where is pvc NOT legal for use?

It must be legal where I am. My PVC is in plain sight, and it was inspected and passed by the gas company man, and three different inspectors: electrical, plumbing, and fire protection. Of course, they also approved my ungrounded, unbonded CSST as well, also in plain sight.

Mark Eatherton

Common culpability...

Chris, you obviously (now) have a dog in this fight (poly propylene venting systems available now), but prior to that, your and your contractors choices were limited to the PVC or SS categories.



What did you USE to recommend to your contractors? Got any PVC venting systems floating around in your closet? I realize that the majority of your systems were Viessmann, and understand their reasons for not allowing PVC, but I also know that you deal in other systems that DO allow the use of PVC. Did you only sell SS pipe for THOSE applications? Did you make the contractors who purchased PVC for venting those systems sign a release of liability form?



I have nothing BUT pvc floating around in my closet, and I have had Z E R O issues, and in some cases, I know it is being seriously abused.



It may not make it right, but I think that the industry needs to fall back and review the application and see if there is an acceptable niche market. Remember, the temperature / pressure ratings that were developed assumed the use of pressurized water. These venting systems are NOT seeing significant operating pressures, hence the tube may be more forgiving under these conditions.



Don't get me wrong. I am all for safe operation of gas fired appliances. I just think this is a witch hunt that is really unnecessary...



To borrow a line from a group (water heater manufacturers) that Dave Yates and I once had a long and arduous battle with, "Show me the bodies!"



This stuff has been in service for well over 1/4 of a century. Why, all of a sudden, is it an issue now?



ME

Mark Eatherton

Been there, seen that...

Inspect it on a regular basis for any major changes, and have seen none.



This system is doing only DHW thru a HTP tank, from a HTP Munchkin. Essentially running at 180 degrees F all the time.



Note that the discoloration is ON the exterior of the pipe, and that immediately under this surface, there is NO discoloration.



This is also located in a downtown setting that has a LOT of automobile pollution in the air. Have not seen this in any of the other appliances I have installed.



No exterior signs of embrittlement, checking, cracking or crazing.



ME

Mark Eatherton

I welcome his participation....

and as usual, we are ALWAYS open and friendly here at The Wall.



Maybe we can ask him why it is that combustion testing of all fired appliances is not in the national codes...



Education and progress is good.



BTW, I have come up with a solution for the chlorides leaching out of the venting systems and rolling back to the boilers, but would prefer to not dilute this topic...



ME

Dave Yates (GrandPAH)

SMTB

You had to go there!?! That phrase still raises my BP(G). I too must confess I've found the PVC issues to be unwarranted from an anecdotal personal experience level. The worst case for us was a supply house telling us it was OK to vent what turned out to be an 80+ furnace with PVC. Seasonal service revealed yellowed & discolored PVC within the first few feet - badly abused PVC temp-wise. Lesson learned: don't let a supply house counter dude tell you what's correct!



However, not one single PVC install on a 90+ furnace, modcon boiler, power-vent, or DV water heater has shown any evidence of any looming danger & we're now past the 20-year mark. I've encountered a few foam-core PVC exhaust vent installations & recently replaced one because we were replacing the modcon installed by another firm. I was pretty surprised to find it appeared to be in perfect condition after so many year of service in a system not utilizing outdoor reset that ran at much higher temps than required (following analysis and adding outdoor reset).



The lone issues I've encountered were all a result of a faulty installation and exceeding the manufacturers' specifications.

Unknown

whats CPVC

maybe?

CMadatMe

The Closet

I would be lying if I said I never sold it as a vent material. Back in the day when the brain began its hunger for knowledge never paid any attention to it. Mfg said is was ok. The funny thing is that in all the classes you never heard them once define ASTM 1785 and state that you should be using another vent method when stack temps exceed 140 degrees. Never one did you hear that PVC was not rated above 140 degrees. Now every class I participate in those are the questions I ask. So me the testing data. Seen plenty of sagging and as you have shown "brown" vent pipe out there.



My stake in poly prop has nothing to do with Viessmann. We sell Triangle, Alpine, PureFire and others. If my hand is in the trigger of the gun then you getting quoted PolyProp and the reason why. You want the PVC that's up to you. I gave you the choice and my reason. I think contractors are fools for not using it from a sales aspect (money in your pocket). Willing to bet informing the customer you are using a tested vent system over your competition with the reason why closes a sale or two. We actually close Viessmann sales in cases just for that reason. Consumers today are more in tuned to the mechanical aspect of their homes then in the past.



Poly Prop is a listed and tested vent system and offered at a reasonable price. We cannot talk price so not being able to share a cost comparision between 2", 3" or 4" PVC is a little disadvantage in proving the cost point.



Could you please show me the deaths from "Plex Vent." I still have guys coming across it in the field and its recall goes back to 1998. Yes we all know it is not safe. The mfgs were smart enough to get together and stopped a potential problem before it happened. Why, because another mfg was holding the money bag not them. In the case of PVC the money bag would be in all their hands since the PVC mfgs have put its use in their hands.



I'm going to Triangle on Thursday and the questions about venting PVC are on on my pad to ask.

Tim McElwain

CPVC is

chlorinated poly vinyl chloride which can operate at a higher temperature than straight PVC.



Maximum operating temps:



ABS Schedule 40                            160 ° F

PVC Schedule 40                             140° F

CPVC Copper Tube Size                   180° F

CPVC Scheule 80                             200° F

pipe4zen

ASTM 1785

Is a testing standard for PVC used for hot and cold water pressure systems. It's rates pvc that at a given temperature and pressure relationship. Any temperature over 73 F has a correction factor multiplier for pressure limitations, but temperature cannot exceed 140 F under pressure.



ASTM 1785 has no authority for combustion flue gases. Just as ASTM 2665 would have no substance also (PVC used for DWV). You keep mentioning this standard , and as you know there is no seperate testing standard as of yet for PVC and combustion flue gas , nationwide.



As long as equipment manufacturer's approve of it, then installer is covered , under law, if proving that it was installed correctly according to equipment specifications.



If PVC piping was a problem, then you would think that the PVC cases that just about all of them have would be a problem, not to mention also, plastic condesate traps, pvc coated wiring running throughout the equipment , etc. But then it probably would not be a 0 clearance unit either.

CMadatMe

I Keep Mentioning

The standard because that is what is listed in all the installation manuals. I know about the correction factors I have them. Those correction factors also clearly show that PVC is not rated above 140 degrees whether at 1psi or 100 psi.

To me that means, if you know your venting will see more then 140 degree stack temp don't use it. Move on to the next vent method provided in the manual.



Is everyone so caught up in the cost of not using PVC? PolyProp which is clearly tested and stamped as a vent system for flue gas temps up to 230 degrees is not that much more then PVC. Its a heck of alot less expensive the Stainless. Ask your next customer which they would want in your next estimate. A vent pipe that is not tested for xx dollars or a vent pipe that is tested for xx dollars. We are talking about between a Mr Jackson and a Mr Franklin depending on the installation.

If the pros stepped up to the plate and began offering it to their customers you would be surprised by the choice of your customer. They will take the vent system all day long. Why do we offer our customers the Alpha's, Wilo's, Taco VDT's, Zone Sentrys and all the other system side components as options but leave out offering a tested, labled and approved vent system?



How many of you have offered your customer an alternative to PVC for venting?

pipe4zen

Safety

That's fine , if a wholesaler, or contractor wants to offer an upgrade to a different venting product. There are dozens of upgrades that can be offered as well, "L" is better than "M" copper, but I'm not going to imply there is a safety concern.



But there currently there is no code violation , state or national, about using PVC sch. 40 pipe for equipment venting. There is no safety issue either, a properly installed and supported pipe. It will not melt or sag.



The manufacturer lists ASTM 1785 , because they want you to use that type of pipe , not PVC cellular foam core, not ABS, not thin wall, because they don't have that ASTM.



The 140F is a limitation for pressure installs, even at 1psi. A vent system has 0 psi. My only wish is that a national standard be given , no matter the outcome, and all installs then comply. Until then, current installs are safely and legally in compliance.



So I agree with you, but also disagree with you.

CMadatMe

I Also Agree With You

That there is no  violation based on code and that there needs to be a standard. I think Canada has given us that path and it should be adopted here.

Tim McElwain

It remains to be seen

as to what the outcome will be with all of this. There are pros and cons among the contractor side of this discussion as is certainly evidenced here.. A lot of that driven by cost of plastics versus stainless steel I am sure.



I have witnessed several times in the past five years PVC and CPVC which show signs of stress from over temperature especially in cases of indirect connection to the boiler system. I have also seen it on vents on warm air furnaces perhaps the result of poor maintenance such as keeping the filter changed, cleaning the secondary heat exchanger at least once a year, insufficient return air. etc.



I was involved way back with the Plexvent and Ultravent fiasco. My company a gas utility that had the responsibility for testing for approval to sell in our state tested both of them. Our preliminary findings found no problem at all with the two products. We did however keep the plastic as a vent system on some of our lab training equipment. I began to notice a change in the fittings especially after about 10 months operation on a continuous basis with classes in the lab firing the equipment every day. After 18 months I brought the change to the attention of my superiors and they viewed my findings but no action was taken. Within a two and a half year period we had to add more hangers to support what was a definite sagging affect taking place. The original support system was to manufacturer specs.It was at the end of three years my company took action to ban future use of it until more testing could be done by the manufacturers. It was several years later it was banned. That product was used by many contractors at the time and most said they had never had a problem. 

TomS

1998 recall on plastic vent

At least in the year 1998 it appears that PVC was not listed in this recall notice.

 U.S. Consumer Product Safety Commission

Office of Information and Public Affairs

Washington, DC 20207

FOR IMMEDIATE RELEASE

CONTACT: Russ Rader

February 24, 1998

(301) 504-0580 Ext. 1166

Release # 98-072       CPSC, Manufacturers Announce Recall Program to Replace Vent Pipes on Home Heating Systems

WASHINGTON, D.C. - In a landmark action, virtually the entire furnace and boiler industry together with the manufacturers of high-temperature plastic vent (HTPV) pipes have joined with the U.S. Consumer Product Safety Commission (CPSC) to announce a recall program. This program will replace, free of charge, an estimated 250,000 HTPV pipe systems attached to gas or propane furnaces or boilers in consumers' homes. The HTPV pipes could crack or separate at the joints and leak carbon monoxide (CO), presenting a deadly threat to consumers.

CO is a colorless, odorless gas produced by incomplete burning of carbon-based fuel, including natural gas and propane. The initial symptoms of CO poisoning are similar to the flu, and may include dizziness, fatigue, headache, nausea and irregular breathing. High-level exposure to CO can cause death.



To determine whether they have HTPV pipe systems that are subject to this program, consumers should first check the vent pipes attached to their natural gas or propane furnaces or boilers. Vent pipes subject to this recall program can be identified as follows: the vent pipes are plastic; the vent pipes are colored gray or black; and the vent pipes have the names "Plexvent ," "Plexvent II" or "Ultravent " stamped on the vent pipe or printed on stickers placed on pieces used to connect the vent pipes together. Consumers should now check the location of these vent pipes. For furnaces, only HTPV systems that have vent pipes that go through the sidewalls of structures (horizontal systems) are subject to this program. For boilers, all HTPV systems are subject to this program. Other plastic vent pipes, such as white PVC or CPVC, are not involved in this program.



After checking the vent pipes, consumers should call the special toll-free number (800) 758-3688, available between 7 a.m. and 11 p.m. EST seven days a week, to verify that their HTPV pipe systems are subject to this recall program. Consumers with eligible systems will receive new, professionally installed venting systems free of charge. Additionally, consumers who already have replaced their HTPV pipe systems may be eligible for reimbursement for some or all of the replacement costs.



       The program came about as a result of mediation among 27 participants manufacturers of HTPV pipes and manufacturers of natural gas or propane-fired boilers and mid-efficiency furnaces. This is the first time that CPSC has used a mediator to bring together all segments of an industry to implement a program for the benefit of consumers.



All consumers should have their fuel-burning appliances inspected each year to check for cracks or separations in the vents that could allow CO to leak into the home. In addition, CPSC recommends that every home should have at least one CO detector that meets the requirements of the most recent Underwriters Laboratories 2034 standard or International Approval Services 6-96 standard.



The following lists the manufacturers participating in this program.



Participants



Armstrong Air Conditioning Inc.

Bard Manufacturing Co.

Burnham Corp.

Consolidated Industries

Crown Boiler Co.

The Ducane Co. Inc.

Dunkirk Radiator Corp.

Evcon Industries Inc.

Hart & Cooley Inc.

Heat Controller Inc.

International Comfort Prod. Corp.(USA)

Lennox Industries Inc.

Nordyne Inc.

Peerless Heater Co.

Pennco Inc.

Plexco Inc.

Raypak Inc.

Rheem Manufacturing Co.

Slant/Fin Corp.

Thermo Products Inc.

The Trane Co.

Trianco-Heatmaker Inc.

Utica Boilers Inc.

Vaillant Corp.

Weil-McLain

Westcast Inc.

York International Corp.



The U.S. Consumer Product Safety Commission protects the public from the unreasonable risk of injury or death from 15,000 types of consumer products under the agency's jurisdiction. To report a dangerous product or a product-related injury and for information on CPSC's fax-on-demand service, call CPSC's hotline at (800) 638-2772 or CPSC's teletypewriter at (800) 638-8270. To order a press release through fax-on-demand, call (301) 504-0051 from the handset of your fax machine and enter the release number. Consumers can obtain this release and recall information via Internet gopher services at cpsc.gov or report product hazards to info@cpsc.gov. This Website is Powered by Online-Access® All Rights Reserved © 2001-2011



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Unknown

aluminum

not acceptible?

Tim McElwain

No it is not

an acceptable venting material as far as I know it never was. We have had galvanized (single wall)  24 to 26 gauge for Category I non condensing and also "B" vent which is double wall also for Cat I.



Are you talking about the aluminum flexible vent for lining chimneys?



Also dryers use an aluminum exhaust?

Jason_13

Other countries

I have read that almost if not all other countries have banned PVC for venting heating appliances. What do we think we know that they do not?

I was told by a European contractor one time that we Americans only think we know something about mod/cons and we don't know ****. They have been doing mod/cons for over twenty years and have learned much in that time but we are too good to listen.

Take it for what it is worth. I wasn't listening.

CMadatMe

Catch 22 Jason

Triangle, Buderus, Baxi all allow PVC over here? The question then becomes, why? You are correct in that they don't use it across the pond. They all use either a Coaxial or Poly Prop.



I do have a question for ME and HR. Why does Lochinvar require CPVC before the transition to PVC? I would ask Glen Stanton the same for the Burnham Alpine? Do these two mfgs know something?