[Greenbuilding] venting a gas water heater into ABS plumbing?

[William R Bloom]

Hi Ruben:

This is one perforation I would think you would want to go 
ahead and make.  First, gas water heaters are historically 
one of the most inefficient appliances in your house.  The 
flue will heat significantly and you do not want to 
introduce heat to ABS.  The polymer is not made to carry 
heated liquid, gas, anything.  Second, there is no 
building code I know of that will approve such an 
installation.  Install without a permit and you might live 
with it for a while, but try to sell the house and a 
building inspector will have you retrofitting it.  Third 
is the chance (probably slim) that a carbon heated glowing 
particle could rise from the waterheater gas burner and 
ignite sewer gas in the vent system.  Fourth, most DWV 
waste vents typically terminate vertically on the roof 
without a cap or other termination device.  As such, rain 
can come down and doesn't cause a problem in a waste 
system, but will in your waterheater combustion system. 
 You could cap it, but then be in risk of a violation of 
the plumbing code as vents cannot be restricted or capped. 
 Lastly, I can't think of a galvanized flue to ABS fitting 
that you could use to tie the two together and hope that 
they would be gas-tight without using a rubber fitting 
also subject to heat.

Bill
Albuquerque


On Sun, 11 May 2008 08:47:23 -0700
  "Reuben Deumling" <9watts at gmail.com> wrote:
> As I am keen to minimize the number of perforations to 
>my building
> shell what would be the reasons NOT to vent my gas water 
>heater into
> the stack that vents my sinks? I certainly don't want to 
>ignite sewer
> gas, but what are the chances of that with such a setup? 
>Or
> precautions one might take to reduce the chances of it?
> 
> Thanks.
> 
> Reuben Deumling
> 
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