can I vent a natural gas water heater and a natural gas hot water boiler out the same chimney from basement?

by Water Heaters on July 31, 2010


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    { 4 comments… read them below or add one }

    PAUL July 31, 2010 at 2:32 pm

    Can we have more explanation please? Are these natural draft appliances? (meaning they vent using metal vent pipe) If that is the case then, yes. They would require an aluminum chimney liner, with the size dependent on the BTU’s of the appliances. In a typical size home, this would be 5 or 6 inches in diameter. The boiler would be connected to the liner using metal pipe with a ‘Y’ fitting for the water tank to connect too, and the water tank vented in aluminum pipe.

    Check with a heating company in your area, this is something a pro should take care of.

    Nomadd July 31, 2010 at 2:32 pm

    Yes. You’d have to have one way flappers in both pipes before they join to prevent the exhaust from one device from going down the vent into the other device.
    It wouldn’t work if the boiler has forced exhaust.

    John M July 31, 2010 at 2:32 pm

    Vent these stacks separately but they can be side by side as far as wall penetrations.
    Reason for not venting the stacks combined is that if one goes out it can allow
    for a venturi suction effect and pull the combustion gases back into your home.
    Safety is your utmost concern. Now as far as the exterior stacks are concerned
    always make one of the stacks a foot longer than the other and give adequate
    length to promote off gassing. Only time you can have them the same length is
    if they are separated by at least 3 feet.

    Mel July 31, 2010 at 2:32 pm

    Sounds like you are asking if you can use an exhisting brick furnace to vent both appliances . Yes you can combine the vents but you must line the chimney with a metal liner first to meet code . If you dont line the chimney the water vapor in the vent gases has is very acidic and starts to eat the mortar in the chimney and that can cause the chimney to eventually fail . Make sure to size the vent for the combined BTUs for the 2 vents .

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