Installed a new water heater last night (Rheem Performance Plus Model #XG50T09HE40U0). All went well with installation (including gas line bubble test), but this morning I could detect a faint smell of gas.

I had re-used the existing gas line last night (except for a new male threaded adapter), but after smelling it today I replaced the line with a fresh one (and reused the new male threaded adapter from last night). All threads were well sealed with thread tape. However, after replacing the line today, I can still detect the smell.

It smells like it's coming from where it is connected in the control unit.


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  • Did you repeat the bubble test after you replaced the gas line?
    – Comintern
    Apr 22, 2014 at 22:33
  • Yep. I didn't even dab it on this last time, I dumped that soapy water all over it. Maybe an official leak solution would work better than the ol' dish soap + water? Apr 22, 2014 at 22:38
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    From @andy: Did you ever find what the issue was? I am having the same issue out my new tank. Second tank a both had a faint gas smell coming from around the Honeywell control box. Jan 3, 2016 at 2:18

3 Answers 3


You have used the wrong type of teflon tape - for gas the thicker yellow teflon tape should be used. Another option which many prefer is to use a pipe sealant like RectorSeal.

If after replacing the white teflon the smell persists I would check the other end of the gas line. It's possible that when removing the old gas line an existing fitting was loosened and is now leaking slightly.

  • Good suggestion. I'll pick some up tonight and replace it. Do you think it's necessary to replace the threaded male adapters since I've tightened them completely once? Apr 23, 2014 at 0:08
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    No, since you have it apart you can inspect the threads for damage but they should be fine.
    – Alex
    Apr 23, 2014 at 0:18
  • I answered too soon. I thought it was resolved, but the gas smell has returned. I replaced the tape with the yellow gas tape (3-4 wraps on all 3 male adapters) and a faint smell is still coming from the connection nearest the control box. I also picked up RectorSeal, so I will try that next. I've read some people use both. I might try just adding RectorSeal around the yellow tape. If it still doesn't solve the problem, I might open the control box to look for a leak in there. Apr 23, 2014 at 23:36

The leak was inside the control box.

I talked to Honeywell, and they sent out a replacement control box. It was a straight-forward replacement. The original was either faulty, or I was too eager while tightening the gas line (e.g. broke it myself). Either way, replaced it, used the correct tape, and confirmed all is well with a gas leak detector. All good.

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    Gas valve assemblies have two 'flats' on them. This is where you back it up with another wrench so you don't torque the whole thing. Also, try to remember that most assemblies are soft aluminum, and you're screwing a hardened steel pipe into it. Only experience will tell you when to stop, and now, that you have ;)
    – Mazura
    Jan 4, 2016 at 12:28

Where the flexible gas line connects to the fitting on the water heater, you DON'T use Teflon (or any other sealant). That is a common mistake made by many people. You don't use ANY sealant on that connection. The flexible gas line has a compression type flare on it. To make sure it is connected tight, use two crescent wrenches, and hold the nipple at the control box with one wrench, and tighten the gas line with the other wrench.

The gas nipple that attaches to the control box on the water heater DOES NEED pipe sealant though.

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