Adding Gas Water Heater Exhaust To Chimney

Tom_22

I have an oil boiler now with a water heating coil. The exhaust pipe is 10" or 12" and enters the base of a brick chimney about 5 1/2' above the basement floor. There is a cleanout access door to the chimney directly under where the boiler flue taps in.

There is some room above the boiler flue. If I wanted to retire the boiler water coil and have a gas hot water heater installed, could the exhaust flue be stuck into the chimney directly above the boiler flue? Are there any other considerations to take into account?

S Davis

Flue

If it is a unlined chimney the waterheater will have a hard time heating up the flue and getting a good draft, it might not draft at all, especially if it is an exterior chimney.
It is allways a good idea to install a chimney liner when installing a smaller appliance that will run by itself.
Also you will need one liner for your gas waterheater and one for your oil boiler.
What about installing a indirect waterheater off your oil boiler?

S Davis


Apex Radiant Heating

lchmb

how about

If you already have a boiler why not add a superstore? Then you would not have to go through the issue's of venting, gas line's, gas check and all. Another consideration is most gas hot water tank's only have roughly a 10 year life span. Some of the newer storage tanks are lifetime guaranteed....Just a thought..:)

DaveGateway

Code in most places

wil not allow you to vent multiple appliances with differennt fuels. Draft will vary greatly from summer to winter when both appliances are firing. You probably have the extra BTU's in the boiler already. Get a nice indirect with priority controls. It will give you plently of hot water and let the boiler warm up and dry out condensation in the summer time.

Jack_21

Yes, you CAN, but you don't want to

Liner comments are correct. Trying to get the flue to draft properly in the months when the boiler is not operating would be difficult, depending upon the actual size and construction of the chimney. a liner would solve that problem but create others.

NFPA 31 does allow venting a gas appliance into an oil flue. Typically it should be mounted 12" above the breaching of the oil unit. In the event there is insufficient height to tie in a ft above, it is also ok to use a wye fitting and tie in as close as possible to the vert portion of the chimney.

lchmb

as long as

The chmney is lined. A gas appliance cannot be vented into an unlined chimney.

Jack_21

Roger that!