PVC Venting

radmix

I was on a project today that I installed a condensing boiler 5 years ago in a new construction project. The homeowner is now adding a substantial addition so I upgraded the boiler size and disconnected the boiler and venting today. All of the air intake piping was secure but the exhaust piping fell out of the fittings that it was glued to. All of the pipe had purple primer and you could see the glue in the fittings but it somehow didn't remain intact. Scary

Steamhead

Despite its frequent use

PVC is not a listed material for venting combustion products. Use something better for the new one. 

HDE

Here we go again

PVC pipe isn't listed by who? It sure is its listed by many manufacturers.

If your talking about ASTM they don't list any appliance vent pipe because that's not their jurisdiction. When they decide to get involved and then say no, then things could change.



PVC type pipes are listed by certain manufacturers under certain installation conditions and they are safety approved by CSA International which includes the venting.



The International Fuel Gas Code states in section 503.4.1.1 (IFGS) “Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer's installation instructions.”

Zman

Details

What type of boiler was it? What temps? How was the piping strapped? How did the pipe look?Was the failure due to heat, expansion, chemicals?

bill_105

Ditto!

I saw this thread from the get go,and my very first thought was "Here we go again".

We play Ray Charles all the time but it's actually a Kingston Trio tune

Hope this helps!

icesailor

Pipe Manufacturer's:

Show me where the PVC pipe and fittings manufacturers list venting appliances with flue gasses over 140 degrees approve the use for exhaust venting?

Charlotte Pipe & Foundry doesn't approve of it. Just because the manufacturer of the appliance says it can be used doesn't mean that the manufacturers of the pipe and fittings approve of it. They may be fine with you buying and installing it but if there is a problem, they are not going to defend you.

Somewhere I have a notice from Charlotte about them not approving it. I may have gotten it from a Veissmann class.

If the exhaust vent is turning brown, the chlorides are leaching out of the pipe.

As far as the pipe with the purple primer coming apart, Massachusetts requires the use of PVC cleaner/primer. It doesn't specify any color. I have only used Clear primer. I know how the pipe and fittings are supposed to go together and how it feels. I always do the pipe and fitting socket. I was in Florida and did an irrigation repair for someone. The only cleaner I could buy was the purple kind. It sucked. With clear, a heavy dose of cleaner will wipe off with a clean rag the purple stuff wouldn't wipe off unless I covered and wiped it a few times. Then, when I cemented it, it didn't "feel" right. I didn't think it set right and I could pull it right back out. Another wipe of cement and holding it together made it better.

I ALWAYS chamfer the end of the pipe so that the pipe doesn't act as a squeegee and wipe the cement from the fitting socket. I don't see a lot of deburring tools in trucks. A "Solvent Weld" is supposed to soften both male and female sides of the fitting by the cement and make it a one piece bond. If it isn't done properly, it isn't a solvent weld connection. You should also check the date code on the bottom of the can. If you don't use a lot of PVC cleaner and cement, it can go out of date. Check the date codes on your PVC cement in your trucks. You might find that it is out of date.

If you don't use a lot of PVC cement, and you but it in quarts because it is only slightly more than a pint, it may be out of date or lost strength through evaporation.

radmix

Venting

The boiler removed was a Munchkin M80, The boiler replacement is a Triangle Tube Solo 110. This is a low temp application all slab radiant max temp 120*. The pipe looked intact but the fittings seem to have came falled apart due to the heat of the exhaust. The intake pipe help perfectly

kcopp

just a thought....

how long after you glued and assembled these fitting did you fire the boiler? Were they still "wet"?  Just a thought.

RobG

PVC Vent

Could you post pictures of the fittings and pipe in question?

HDE

Hmmmm

I'd like to see too.

Furnaces, water heaters, boilers have used PVC for years yet a low temp boiler application doesn't hold 1 solvent weld?

icesailor

PVC Venting:

I've installed more than a few Munchkins and I've seen a lot of them installed. I've never, ever seen anything like you have described.

Last week I removed a RUUD PVP-50 that I installed in 1995. It was vented with Charlotte Sch. 40 PVC pipe and fittings. The pipe was tan now and was white before. There is no way that I could have gotten any fitting off the pipe. The inside of the pipe and fittings were stained black. Not soot, but black.

You must be dealing with an anomaly. And like i said before, I've had "an experience" with purple dyed cleaner. Perhaps you used cement that was out of date.

Just a thought.

radmix

Venting

Sorry, Its all in the dumpster. Ive used PVC venting on over a hundred installs also but I had never had the chance to take it apart.

icesailor

PVC Venting:

The only plastic venting I have ever seen fall apart was Plex-Vent and the other gray stuff where the clips rotted away and RTV sealant couldn't hold it all together.

I've never been able to get ant PVC apart. Plumbing or heating. The only way I have ever gotten a piece of pipe out of a socket was with a Ram Bit.

Henry

PVC

First, any plastic venting that I have seen that was defective was due to using old glues. We always install a plastic vent with a new can of primer and glue. Here is Canada, we have S636 PVC Sch 40 approved venting. The S636 standard is just a new colour and new labeling of standard Sch 40 PVC and CPVC pipe.



The appliance manufacturers have tested their product with various venting materials to get CSA or UL approvals. If properly installed, it is safe. As in nearly all cases of failures, it was the installer who screwed up.

Mark Eatherton

Old or Frozen cement???

Most people don't realize this, but there ARE limitations in the temperature that these cements are supposed to be exposed to.



My brother, also a master plumber, had a design on a storage box for vans that was lead lined (for momentum mass) and had a small electric heating element in it to guarantee that the cement was not exposed to freezing conditions. He changed careers and never finished pursuit of a patent.



I wonder how many service techs have a "hot box" that they remove from their van (if stored outside at night) to keep their cements and primers nice and warm...



I'm with Henry, the cost are so low, that it warrants purchasing new, every time you do an install.

HDE

Get the facts straight

I chuckle everytime a misinformed person starts spouting off about Sch 40 PVC temp limitations. They always use the rating provided under pressure, and think it is 140 degrees fahrenheit. I have news for ya, vents systems have minimal measureable pressures.



Heres the real numbers:



According to PVC Pipe and fitting manufacturers, PVC has the following ratings:

Maximum Temperature: 158°F, 70°C

Minimum Temperature: -13°F, -25°C

Melting Point: 176°F, 80°C

Tensile Strength: 6,500 psi

TonyS

Cleaner and primer

are two different things.

Primer containsTetrahydrofuran... cleaner does not.

Cleaner will not remove the glaze from the pipe or fitting and cleaner is only for cleaning dirty pipe.

Primer can be colored purple.... cleaner cannot. Both are available uncolored.

I have seen guys use primer to remove pipe dope and cutting oil and then stick it back in their van to use on pvc later.

There is a little science to this otherwise simple task.

I love hearing about how sloppy purple primer is.. primer is an inanimate object so that only leaves sloppy mechanics!

radmix

Venting

It could have been older glue its hard to remember 5 years back. But again like I wrote before, The intake was fine only the exhaust.

kcopp

Odd things happen....

I removed an old leaking power vented tank type water heater , vented in PVC, two weeks ago. I started to disassemble the 3" venting, only to realize every joint was dry fit together on all the joints..... no glue at all. The install was 8 plus years old.

birdsalljoed

PVC pipe for Vent

Many if not all boiler manufacturers list sch40 PVC as an option for venting. However, the PVC pipe manufacturers have, not to my knowledge, given their blessing. Some manufacturers including Peerless and Weil Mclain have recently approved a polypropylene venting material for their condensing units. www.centrotherm.us.com. hope this helps.

Henry

ABS

BTW, solid core ABS has a melting point of 217F! A good read is TR-19/2000 about thermoplastic piping by The Plastic Pipe Insitute. One thing overlooked very often is teh expansion of the product used. I have seen split elbows at the bottom of chimneys when vented through the side of the chimney some 50 plus feet.



A neat trick to keep the plastic vent from leaking in the chimney chase: use a rubber 3 or 4 inch roofer vent  flashing. It keeps a tight fit and allows for pipe expansion.

HDE

And

And the weight alone since its near impossible to support 50' inside a masonry chimney

Gordan

ABS vs. PVC

One thing to keep in mind is that ABS has nearly twice the thermal expansion of PVC.