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Thread: Gas leak on control valve unit

  1. #1
    DIY Junior Member lumberjack's Avatar
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    Default Gas leak on control valve unit

    I put in a replacement gas water heater recently; the installation went well, and the heater works great. It's a Whirlpool N40S61-403 natural gas model with a Honeywell control unit. I obsessively leak checked all the gas line connections to the heater several times with no issues found. Unfortunately, if you put your nose right next to the control valve unit, there is a light whiff of gas. This is in an attic, with a lot of airflow, so you really have to get close to the control valve to notice the gas. A foot away, there is no odor. It's obviously a minor leak, but not acceptable.

    I ordered a gas detector/tester, and got up to the attic to do some testing today. As expected, the gas lines and all connections are fine, but the detector begins clicking faster when I put it near the top seam of the plastic cover of the control unit. I took the cover off for more detailed testing, and was able to pinpoint the leak to a molded "spout" (for lack of a better word) on the front of the control unit. It has what looks like a pressed in plug with a small orifice (a little bigger than a pinhole) in the middle. If I had to guess, I'd say it's part of a valve or relief. There's also a concentration of gas coming from the back of the unit, but it is likely spillover from the main leak.

    Here's a video of the testing:



    I am going to call Whirlpool tomorrow and see what they can do for me under warranty -- I assume I will need to install a new control unit. But I was wondering if anyone has run into an issue like this before, and if there's anything else I should check or test. I might be inclined to tighten up the manifold and pilot tube joints going into the control unit, but they really don't seem to be leaking according to the tester, and I hate to randomly re-tighten a fitting without a good reason.

    Thanks for any help you can offer!

    Al
    Last edited by lumberjack; 04-01-2012 at 05:24 PM.

  2. #2
    DIY Junior Member lumberjack's Avatar
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    Just got off the phone with Whirlpool support -- they are overnighting me a new gas control valve. Not looking forward to tearing into a new install, but it doesn't look like too much of a project to replace the valve, so hopefully that solves the problem.

  3. #3
    DIY Senior Member Runs with bison's Avatar
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    It is not unusual to smell faint amounts of gas on the older Unitrol units (including replacements) near the plastic dial. I've read others reporting it which is why I checked after passing bubble tests on connections, and found I could detect a faint seep on the new valve assembly at one of the dials. I don't know how sensitive the tester you are using is by comparison. Mercaptan is easy to detect by nose so I'm guessing your results on a newer valve type were far worse than mine.

    Hint: Shut off the heat first, then take a shower (and encourage any other occupants to do so as well) before starting work since you cant be certain when things will be right again. That way you have less hot water to drain before it cools off. And do this on a week night if you can rather than leading into a weekend...in case you have unforeseen problems.

  4. #4
    DIY Junior Member lumberjack's Avatar
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    Quote Originally Posted by Runs with bison View Post
    It is not unusual to smell faint amounts of gas on the older Unitrol units (including replacements) near the plastic dial. I've read others reporting it which is why I checked after passing bubble tests on connections, and found I could detect a faint seep on the new valve assembly at one of the dials. I don't know how sensitive the tester you are using is by comparison. Mercaptan is easy to detect by nose so I'm guessing your results on a newer valve type were far worse than mine.

    Hint: Shut off the heat first, then take a shower (and encourage any other occupants to do so as well) before starting work since you cant be certain when things will be right again. That way you have less hot water to drain before it cools off. And do this on a week night if you can rather than leading into a weekend...in case you have unforeseen problems.
    The Whirlpool tech told me that it would have been normal to smell a faint amount of gas on the older model heater controls (consistent with what you're saying), but that I should not be smelling any on the new Honeywell controls. I plan to take a close look at the new control when it shows up today, and see if there are any obvious leak paths that I could maybe snug up on the old control before I tear it off the heater and proceed with a full replacement. You never know. Of course, if it's on the backside, I'd have to take the old controller off anyway.

    Thanks for the advice on planning the work -- I have been thinking about how to do things so that I am not draining 40 gal of fully hot water. The added complication of having this unit in an attic makes it a real chore to work on, and minor problems can turn into a multi-hour project pretty easily.

  5. #5
    Plumber jimbo's Avatar
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    Turn off the gas and run water for 10~15 minutes...you will have cooled off the contents of the tank, so you can drain it.

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