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Thread: Water Heater Pilot Is Blowing Out

  1. #1
    Join Date
    Dec 2003
    Cincinnati Ohio

    Question Water Heater Pilot Is Blowing Out

    I changed the WH flue pipe from 3 inches to 4 inches to meet local code and ever since I made the change last week the pilot light has been getting blown out on occassion. The 4 inch pipe runs from the WH and is adapted to the original 8 inch flue pipe that used to also vent the furnace. The furnace was replaced about 15 years ago to a high efficiency unit that uses PVC pipe to exhaust and provide combustion air. The WH was out this morning and when I went to relight it I noticed that cold air was falling down into the burner area. Temperature was about zero and when I got the WH to light and then turned the thermo up the flame didn't want to vent up and out of the flue but wanted to back out from under the burner area. I guess if I had let the flame burn long enough the flue would have warmed up sufficiently to start venting properly. I shut the WH down until I can resolve this problem. Do I need to go back to the 3 inch flue even though it won't meet code?


  2. #2


    I suspect your pilot light needs cleaned. After cleaning your pilot orfice and reinstall it then make sure the thermocouple is directly in the flame of the pilot.

    If still having trouble replace the thermocouple.

    Good Luck


  3. #3


    I fully agree with the pilot light cleaning idea. If that doesn't offer any help, you might want to adjust (or cause to have adjusted) the pilot burner pressure. There is an adjustment for this purpose on the main gas valve. It might need a little more pressure to have a decent enought flame to overcome the occasional gusts of wind down the stove pipe. The data plate of the water heater lists the proper pilot burner pressure in inches of water column ( "wc).
    "Nothing is foolproof to a sufficiently talented fool"

  4. #4
    Join Date
    Dec 2003
    Cincinnati Ohio

    Smile Fixed Water Heater Pilot Light Blowing Out

    Fixed the problem last night. Changed the WH exhaust vent back to 3 inch all the way up to the original 8 inch exhaust stack. Everything works fine now. Guess the 4 inch vent was just too much pipe to warm with the pilot and to keep the cold air from falling down. Thanks to all for your help.


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