My water heating tank has sprung a leak - out of the top (fortunately?) Whoever installed this thing didn't do a proper job of preventing galvanic corrosion, so the tank input is corroded (irreparably, I believe) and leaking.

I turned off the cold water input but am anxious about the gas line. Is there harm in leaving the gas on? I guess I'm worried about having to turn it back on and deal with igniting the pilot light, though I don't think that's likely, the tank must be replaced ASAP and I won't be using it again in its current state.

There are a couple images attached - you can see where water has been running away from the corroded input. In one image, on the left you can see the gas line for the furnace - there's a similar line just above for the water heater. Presumably I can just turn the knob to turn off the gas - should I turn it off on the tank, too? The tank has a knob with positions marked "off", "pilot", "on". Turn off the mainline first and let the pilot burn the remaining gas in the line before turning off the gas on the tank itself?

Can this be repaired? The tank will be 12 years old around November and is still under warranty, but I don't think that will cover poor installation. I only moved in within the last year, wish I'd caught this during the walkthrough. The mortgage includes a home warranty, but it doesn't cover corrosion!

Corroded cold water input on hot water tank Contrast between hot water output and corroded cold water input on hot water tank

  • 1
    That corrosion might be from just a seep. The water heater might be OK to use as is until a convenient time to replace it. A 12-year-old gas fired tank WH is due for replacement. May 20, 2019 at 18:56
  • @JimStewart - but what about fixing the leak? It's become substantial.
    – Matt
    May 20, 2019 at 18:58

1 Answer 1


The straightforward solution is to call a plumber to replace the heater. If you are not skilled at sweating copper and have the equipment, then this job is too difficult.

If I were going to repair the leak without turning off all the water to the house, I would cut out enough of the tubing on the tank side of the valve to allow unscrewing the copper female adapter. Then clean up the threads and solder up a new fitting with tubing so that you are not heating the water heater tubing. Then screw it on and finish by soldering the other end.

Before cutting into the tubing, you would turn the gas at the heater to pilot, then turn the cold supply off. It appears the leak is on the cold supply side. Open a hot tap somewhere to relieve pressure in the tank and drain the tank down a little.

  • Do you think the corroded threads on the tank can be salvaged, or would it require detaching the copper and doing some cleanup and investigation?
    – Matt
    May 20, 2019 at 21:27
  • 1
    It would require detaching the copper and cleaning up the threads, and it might not work. It might still leak, and you wouldn't know until you had it all put back together. May 20, 2019 at 21:57
  • 2
    Count on replacing the cold water supply valve. The valve in place appears to be a brass gate valve. You can probably shut it off but then you might not be able to reopen it. It might not shut off completely and then to proceed you'd have to shut off all water to the house. My advice is to call a plumber. Ask him to bring a 3/4" ball valve for the cut-off. And bring bendable supply lines with thread-on and "dielectric" connections. May 20, 2019 at 22:03
  • 1
    You might well be able to do the installation without sweating (soldering) using shark bite connectors such as lowes.com/pd/…
    – Yehuda_NYC
    May 20, 2019 at 22:13
  • Yes, get all the parts to install a new ball valve which connects with compression fittings and a bendable connection line from the valve to the tank. This has a seal and only uses the threads to hold the joint tight. Turn off the water to the house and cut the copper tubing above the valve and install the new ball valve. May 21, 2019 at 2:48

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