Should PVC VENTING BE PROHIBITED ON GAS APPLIANCES

Chowdahead

Zman

It looks like that is cellular core, so absolutely not.

Chowdahead

‘‘Product liability questions abound – If the manufacturer of the PVC piping system does not recommend, warrant or condone its use for venting applications, who do you suppose warrants the system and is liable in the event a failure occurs and property damage or injuries result? The appliance manufacturer? The certification agency? The installing contractor? Everyone in the chain (as is the typical posture of many Plaintiffs’ attorneys when incidents occur)? (Depending upon the PVC manufacturer’s posture, he may be the least liable!)
If you are intrigued by these issues, you may wish to contact the manufacturer of the water heater or boiler (who’s instructions permit PVC to be used) and ask them whether they warrant the vent system and assume any responsibility for any problems that occur. (It is highly unlikely they will respond affirmatively verbally - let alone in writing!)’’

The appliance manufacturer knows beyond a doubt that PVC pipe manufacturer’s clearly state in their warnings “ Not to used for the venting of combustible gases” but the appliance manufacture continues to include the venting in their installation manual.

Bottom line we are installing sewer drainage pipe to vent gas fired appliances .

Steamhead

We don't exhaust with PVC, for that reason. There are better, UL-approved choices.

Zman

@Chowdahead

I knew you were baiting this conversation and I like your style.

I recently had an argument with a mechanical engineer on a commercial job. I wanted him to forbid PVC in the scope so all bidders had to price the correct venting. He indicated that the manufacture allowed PVC venting so it would be OK. I then asked him if he would approve a submittal that highlighted the fact that the PVC manufacture specifically disallowed the use of their product for venting and a specification that was lower than the operating point of the boiler.

We ended up compromising and specifying CPVC.

Not perfect but progress non the less

RayWohlfarth

I have always been leery of using PVC to vent simply because of the temperature ratings. I was taught PVC is rated for 140 degrees F. If you are using a condensing boiler on a system designed for 180 degrees at the outdoor design temperature, the flue gases will be higher than the 140 degrees F. I am not sure of the temperature limits for PVC. I think many people are using polyproylene pipe as it is rated for over 200 degrees F.
@Chowdahead I would like to see a disclaimer by the PVC manufacturer. I have heard about it but never saw it.

Zman

It looks like Charlotte has backed off the combustion vent language recently.

Zman

The venting pictured is cellular core....

EBEBRATT-Ed

From IPEX website

PRODUCT DETAILS


TOP RESOURCES


SPECIFICATIONS


CASE STUDIES



































PRODUCT DETAILS



ONE CODE CHANGE, TWO CERTIFIED SOLUTIONS

We offer System 636 in two distinct materials (PVC & CPVC), each with a unique temperature rating. These venting systems are approved as Type BH vents and are designed for negative or positive pressure venting of gas-fired appliances.

SYSTEM 636 PVC

System 636 PVC is classified as Type BH Class IIA vent, suitable for use on appliances with flue gas temperatures up to and including 65ºC (149ºF). Sizes include 1-1/2", 2", 2-1/2", 3", and 4". Colored white with unique blue certification markings, System 636 PVC pipe is made to sturdy Sch. 40 dimensions to provide a strong, rigid pipe for the application. A full range of System 636 PVC vent fittings and accessories are also offered.

SYSTEM 636 CPVC

System 636 CPVC is classified as Type BH Class IIB vent, suitable for use on appliances with flue gas temperatures up to and including 90ºC (194ºF). CPVC sizes include 1-1/2", 2", 2- 1/2", 3", 4", 6" and 8". Colored grey, System 636 CPVC pipe is also made to Sch. 40 dimensions to be tough enough for the application’s demands.


SYSTEM 636 CEMENTS & PRIMERS

System 636 PVC & CPVC solvent cements are specifically formulated and certified for flue gas venting applications. We also offer a PVC & CPVC Primer for applications where the gas venting system is to be installed in temperatures below 0ºC (32ºF). A certified Transition Cement is available for connections to ABS appliance connectors.



ADVANTAGES:
•Fully certified as a complete pipe, fittings and cement system
•2 system options cover a broad range of operating temperatures
•No mixing clause of ULC S636 ensures full compatibility of all pipe, fittings and cement
•Installer training available

Steamhead

There have been two major wrongful-death lawsuits that I know of where PVC vent pipe failed. One was in Ocean City, MD at the Days Inn and the other was in Colorado.

Sure, PP or SS venting is a little more expensive, but not nearly as expensive as a lawsuit.

HVACNUT

@Zman, looks like Charlotte gets their cake and eat it too. They covered their butts. And if the manufacturer says its ok, then Charlotte Pipe won't refuse your money. Gotta keep the Board happy.

Jean-David Beyer

I an not a heating contractor. I have a W-M Ultra-3 mod-con with an indirect fired domestic hot water heater attached. It has ourdoor reset connected. According to W-M, PVC pipe is OK for both the combustion air supply (no surprise here) and the exhaust.

Design temperature here is 14F outside, but I have had it get as low 2.8F for a few hours one year, so I have set my reset to go all the way down to 0F. Radiant heat with slab at grade, with supply from 80F up to 130F. Upstairs fin tube with supply from 120F up to 150F. The indirect is set for 190F supply but it reheats so fast that by the time the supply reaches 190F, the heat call ends, so it is not so hot most of the time.

The system was installed in April 2009. It has received maintenance every year since. The color of the PVC pipes has not changed at all. When I feel it with my hand, I can feel that there has been heating done, but it is by no means hot.

EBEBRATT-Ed

@Jean-David Beyer
You bring up a good point. While I agree with some posters that PVC may not be the best venting material when stainless steel and PP are available chances are in a system that is properly maintained (like yours) there is probably no issue with pvc.

However as contractors we have all seen systems that are not maintained at all. They get started up and run until thy self destruct.

God forbid standing in front of a judge trying to explain why the cheapest material was installed

Solid_Fuel_Man

The only discolored PVC vent I've seen just like those pictures (pipe darkened and fittings still white) was running on LP and had not been converted from NG! There are literally hundreds of installs I've seen with many years on them where the PVC vent still looks good.

I don't install it, I use PP. That said it was SIGNIFICANTLY more expensive. Several hundred dollars vs. less than $25 if done with SCH40 PVC. The appliance adapters are a big killer, especially for boilers made to directly accept PVC. It's funny that all the internal venting material in boiler case is made of PP though.

Plus no one at all keeps any PP in stock, had to order and a few fittings came in wrong. One supplier carries one brand of PP and another supplier another, with no interchange between brands. I just order online now.

Bottom line: it is more money, more time, and more frustrating. Even the Viessmann dealer couldn't get it all, and we all know V doesn't allow PVC.

Zman

You can see the word COEX CELL..... in the top picture. Cellular PVC is not approved at all. That is why it is yellow.

NY_Rob

Solid_Fuel_Man said:

...Plus no one at all keeps any PP in stock, had to order and a few fittings came in wrong. One supplier carries one brand of PP and another supplier another, with no interchange between brands. I just order online now.



Bottom line: it is more money, more time, and more frustrating. Even the Viessmann dealer couldn't get it all, and we all know V doesn't allow PVC.

I found exactly the same thing when setting up my mod-con 2 years ago. My guy at the local supply house (where I purchased the boiler) looked at me like I had two heads when I started asking about PP. They had some straight sections... but literally no fittings in stock... so how are you supposed to connect it and/or negotiate turns, etc... without fittings? And, the fittings were special order... so any unused pieces couldn't be returned.

I settled for SCH40 PVC (Charlotte Pipe) , my exhaust length is 42" to the outside wall and I made sure it's in plain sight so I can keep an eye on it and inspect it any time I want.
In two full years of use now- the only discoloration is on the short exhaust section that's outside the house (on the south side) which gets full sun all day even in the winter. The intake pipe has not discolored at all in two years, not even the outdoor section.

Bob Harper

This has been discussed in The Wall several times. Pls. search archives.
IRC calls for positive vent pressure venting to be listed. Later, it sorta' contradicts itself by allowing you to follow appliance mfr.s instructions. Most mfrs. still allow polymeric cemented joint venting. UL 103 looked at Canadian S 636 but can't adopt it in US. Too many questions. Note that the reporting system in US is almost non-existent. If you find a failed glued joint or PVC pipe do you report it to the CPSC? What is your procedure for a commissioning test and inspection prior to placing equipment in service? We saw in Aspen, CO the effects of missing cementing joints with the Lofgren case. There is no acceptable test protocol.

What we do have is suitable listed alternatives. UL 1738 tests for positive vent pressure applications. You can choose btw AL29-4c ss venting vs. polypropylene and offer your client a listed venting system vs. you being the mfr. and installer of the venting. What is the warranty on PVC venting?

FYI, those black couplings on power vented water heaters are not neoprene--they're flexible PVC. I spoke with an engineer at Fernco who confirmed this and the fact they know mfrs. are using their fittings for combustion venting applications where it has not been tested or approved but they sell them anyway with a note not to do it.

HDE

Zman said:

It looks like Charlotte has backed off the combustion vent language recently.

They always had the follow the manufacturer requirements. Most quoting letter chose to ignore its last paragraph.