Flue for a propane WH

KD · Apr 16, 2008

Have a propane WH mounted under the house in garage. For the flue, is there a rule as to how many feet horizontal you can go before you go vertical up to the roof? In the horizontal run, do you make it 1/4 inch per foot slope same a sewer line?

Redwood · Apr 16, 2008

Sorry I don't give advice on gas...

Sponsor · 2022-01-29T12:20:58-0800

Lakee911 · Apr 17, 2008

Then why did you even post, Redwood?

Ked, I would make it slope upwards as much as possible. If you don't get enough slope or you have a very long run you may get condensation in that flue which can lead to it rusting out. You can use B-Pipe to get around that as long as you are getting lift to get the gases out. If you're not a draft inducer may be needed, but I'm not sure if you can use these with a WH unless it's a power vented model.

Redwood · Apr 17, 2008

Lakee911 said:
Then why did you even post, Redwood?

Ked, I would make it slope upwards as much as possible. If you don't get enough slope or you have a very long run you may get condensation in that flue which can lead to it rusting out. You can use B-Pipe to get around that as long as you are getting lift to get the gases out. If you're not a draft inducer may be needed, but I'm not sure if you can use these with a WH unless it's a power vented model.

The picture above is the best advice I can give a DIYer on a gas installation!
There are many serious ramifications that can occur from misinterpretations of advice. The advice I gave is the only safe advice to give!

Spaceman Spiff · Apr 17, 2008

I would read the instructions for the heater. I have seen many different rise / run / elbow combinations in the same brand of heater, or of the same type. It all depends on the manufacturer, design, and how they tested it. Let the manufacturer tell you what is safe for their product.

MACPLUMB · Apr 17, 2008

I Would Go With Redwood On This ! !
If You Have To Ask This Question It Shows You Should Be Using A Professional Plumber/hvac Not Trying To Guess Or Ask A Bunch Of
Blind D. I. Y. Who Don't Know Any Thing About The
National Fuel Gas Code Or The Proper Way To Vent Gas

KD · Apr 18, 2008

This was seen on a house inspection for a friend. I recommended that an earthquake strap be installed, T and P drain line be run to the soil and that a licensed plumber inspect the WH flue.

Flue for a propane WH

KD

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Redwood

Master Plumber

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Lakee911

I&C Engineer (mostly WWTP)

Redwood

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Spaceman Spiff

Architect

MACPLUMB

In the Trades

KD

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