Gas Smell from Water Heater

I can smell gas near the exhaust at the top of the gas water heater (Dux 135L) right after the flame goes out. Its not very noticeable, i only discovered it when a friend came over. But i can definitely smell it now. The pilot light stays on and everything works fine. Is this normal? I found a post here talking about the gas smell as if it's normal for all gas appliances. Someone in that post talked about pilot light too, does it mean it will burn the residual gas if the concentration starts to build up? I can't really smell anything when it's on.

Edit: found the post I was referring to



    Minor gas leak - call a plumber and get the hot water system serviced. It’ll be fine.

  • +5 votes

    Put some soapy water (washing up liquid) around the gas pipe connections (where 2 pipes join). You will soon see if the connection is leaking as it will blow bubbles.

    • +1 vote

      Thanks I did that, and I don't see any leaks, I don't really smell anything when the main burner is not working though
      Someone mentioned it could be incomplete combustion. I may call a gasfitter just to make sure. It must have been like this for ages though..

  • +3 votes

    Im a gasfitter and what your describing sounds normal. The pilot is not there to burn residual gas its there to ignite the main burner as the temperature drops below the thermostats settings. If the gas smell isnt there while the main burner isnt running Id suggest you dont have a problem but if your unsure the safest thing to do would be to call a gasfitter.


      Thanks Dr Pid, I can only smell it when the main burner just stops running. It disappears shortly after, and I don't smell it before either, couldn't find much info on the internet

  • +1 vote

    Prodigy Dux gas heaters have a flue damper system. Think of it as kinda like a chimney that opens at the top when the unit is heating water and closes when it is not. To get an idea, watch this video. Around 0:24 the flue damper kicks in. The flue damper is controlled by gas flowing in the 2 small copper pipes shown in the video on the right side of the unit from the base leading to the top. There could be a small gas leak from the flue damper system. Do you know if the anode for the hot water system was changed before? The flue damper first needs to be removed when changing the anode of the gas heater so someone may have incorrectly re-installed.


      Thanks! My unit is Prodigy 3 which was an older version. This could be the problem, I can smell the gas at the top. I don't think it has been replaced but it probably fully sacrificed.. It may need to be serviced.

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