Thread: ABS Flue Pipe on LP Water Heater

Never seen this. Granted, I have only performed about 150 inspections but...
I have seen high efficiency furnaces / boilers with PVC exhaust but never a water heater with ABS... See photo. Any reason this is not acceptable? Also the entire set up is in a basement and the abs has about a 15' horizontal run before it daylights. It is fan assist exhaust but ABS?
(Please ignore extension chord...entirely different issue.)

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Originally Posted by Trey Humphreys

Never seen this. Granted, I have only performed about 150 inspections but...
I have seen high efficiency furnaces / boilers with PVC exhaust but never a water heater with ABS... See photo. Any reason this is not acceptable? Also the entire set up is in a basement and the abs has about a 15' horizontal run before it daylights. It is fan assist exhaust but ABS?
(Please ignore extension chord...entirely different issue.)

Can't say I have ever seen it either. ABS is not approved for any type of gas appliance that I'm aware of.

This from a Rheem page at http://waterheating.rheem.com/Docume...PVGuardian.pdf

Flexible Venting
Options

•

Long venting lengths up to 100 feet

•

PVC, ABS, or CPVC vent pipe options

• Vertical or horizontal termination

(my red)

Gotta say I would be doing a double-take too, but it seems it is OK.

I just looked up that same link. Surprise of the day!

WOW! I agree... Surprise of the day!
Thanks!

I learn something every day.

I see them all the time out here on new construction.

Sorry guys, I didn't take a picture of this one, but the basic question is whether PVC is considered a combustible material.

I was in a 50 year old house today. It had a one year old water heater in the basement using the original venting. Single wall vent up to about a foot from the floor where it changed to a type B vent that had about an inch of clearance to the wood. No problem.
Somewhere in time the owners installed a high efficiency furnace next to the water heater and the PVC furnace combustion air intake passes about one inch away from the single-wall section of the water heater vent.
I have been looking for combustibility of PVC and the best info that I have found states that it will ignite at somewhere between 390 and 540 degrees (150 - 300 degrees higher than wood). What is considered "combustible"?
I had a very understanding buyer and we wgreed to both go away and do some research.

thank you for any help

PVC is combustible, but stop worrying about the temperature it burns, and start looking at clearances.

Single wall vent pipe has a much higher clearance requirement. Tables are listed online.

Dom.

Its been a long time, but I think I have seen ABS on some of the very early direct vent water heaters. I also recall seeing black corrugated plastic tubing, which was supplied by the manufacturer-not a DIY installation.

As with all combustion appliances, get the make and model then look up the manual for answers on suitability of materials.

As for clearances to combustibles, ALL polymeric pipe and venting should be treated as combustible since they cannot pass ASTM E-136. The stated clearance off single walled unlisted vent connector is 6". That includes foam insulation attached to water pipes btw.

The power vented water heater with the integral draft hood is one of the most dangerous combustion appliances you can find due to its propensity to spill CO. Aside from it spilling CO, note that mess of red RTV silicone where it connects to the appliance collar. What a mess!

ABS has a higher service temp. than PVC but neither is listed for use as gas combustion venting in the US. It is a conundrum with the codes, which require all venting for positive flue gas pressure to be listed only to look the other way when an appliance mfr. states it's ok to use plastic venting.