I woke up today to a full drip pan under the gas water heater and my utility room slowly flooding with water. Of course the drip pan was never connected to a drain and overflowing.

After shutting off the water to the water heater the flooding stopped completely. I did some investigation and noticed whenever I manually open the top mounted pressure valve I can tell that some water is discharged through the connected pipe, but I can also hear an amount of water flowing down somewhere inside the water heater. I cannot see any water or wetness when looking closely at the valve connection at the top. I am not sure where the water could be leaking inside the unit. The relief valve is connected to pipe that does not drain into the pan btw. It leaves the room through the wall behind the water heater and does not show any signs of leakage.

Could it help to replace the pressure valve? Is it likely there is a hole in the tank somewhere, but if so why doesn't it leak all the time but only when I open the pressure valve?

I am planning to buy a pressure meter today and check the house water pressure as well as test the pressure on the heater when I reopen the water supply. Will update later with readings.

*Update: I did test the pressure and the house pressure was a little high (75psi, which I now lowered to 65). I also found where the water comes into the drip pan. It is right from the burning chamber, but again, it only flows when I open the pressure relief valve on top of the unit. I can also hear air bubbles moving up while having the relief valve open, so the outflow is replaced by air. (See new photo with markings)

Added photos:

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Original Photos:

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  • It's not clear to me why you think that your water heater only leaks when you open the pressure valve. When you open that valve, water obviously comes out of the water heater through the valve, and any water which comes out is then being replaced into the water heater through the inlet. This is normal operation...
    – brhans
    Jun 8, 2020 at 23:45
  • Have you figured out where the water in the pan originated? Does the "pressure valve" (it's actually a temperature & pressure relief valve) outlet pipe lead into the pan? I ask this because a leaking T&P valve is a common occurrence, while a leaking tank on an 8 year old heater would be very unusual. Can you see dripping water from the bottom of the heater, or from the T&P valve outlet tube? Jun 8, 2020 at 23:58
  • Unrelated, where does that vent pipe go? That is single-wall vent pipe and not suitable for passing through walls/ceilings/roofs... Jun 9, 2020 at 0:01
  • 1
    @brhans: Like I wrote in the question, the pipe connected to the valve does not lead to the pan but to a drain inside the wall, so there is no connection from the valve outlet to the pan, where water accumulates when I open the valve.
    – user118367
    Jun 9, 2020 at 1:40
  • 1
    @JimmyFix-it: I found where the water comes out underneath from the burning chamber (see added photo). Is it worth draining it and taking off the top in order to to get a better look at whats going on around the pressure relief valve?
    – user118367
    Jun 9, 2020 at 3:10

3 Answers 3


Check the age of the tank. The lining is most likely leaking. The pressure vent doing what it is suppose to do, When you manual release the pressure through that valve, water is allowed to escape. The real leak is in the lining, and dripping down to the bottom of the tank. If the bottom is above your drain pan, you should be able to water dripping from the bottom of the tank.
Replacing the relief valve is not going to fix the leak. It was leaking before you touch the relief valve.

  • Thanks for the answer. According to the serial no the water heater is only 8 years old.
    – user118367
    Jun 8, 2020 at 23:43
  • If the lining were compromised, the water would still need to get through the steel tank wall... Jun 8, 2020 at 23:54
  • "only 8 years". Most warrenty on hot water tanks have 6-10 years warrenty. With some high end models going to 10-12 years. To meet warrently requirements, requires some maintenance such as sediment flushing and checking the anode rod about every 3 years. Hard water will shorten the life especially if the flushing and anode replacement is not being done. Jun 9, 2020 at 19:59
  • Turned out the tank had developed a regular leak (see my answer below)
    – user118367
    Jun 12, 2020 at 9:05

It turned out the heater was leaking in general. After some more trial and error the leak started when the pressure relief valve was closed but the cold water supply line nut was losened slightly (so that air could get into the tank). And after the pressure was reduced more the leak just kept going no matter what.

So for some strange reason the tank pressure was holding something in place that was plugging the leak from the inside (maybe sediment?).

I assume the previous owners didn't maintain the water heater properly (we bought the house 2 years ago). There is also a chance the water softener we installed accelerated the decay.

I drained it, uninstalled and will replace with tankless model ($900 gov. incentives for me right now). That should go along with our water softener. Unfortunately the model I want has a two week delivery time. No hot showers for a while...


I’m not too shure but if you turned water off and it’s no longer leaking dry it all up turn it back on run some hot water so it starts to run then see if you can spot it ?? Don’t know how long it’s been leaking but check color of water or any discoloration around it but it’s probably gd gd unless you had some work done around it/ flooring check bottom of it if still nothing

  • I will try that, thanks.
    – user118367
    Jun 9, 2020 at 1:49

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