When we use water in our house like the shower, dishwasher, washing machine, the next time we use the water the pressure is very high for a few seconds. It is causing my hot water tanks pop off valve to open. We have to empty a bucket of water all the time because of this. This hot water heater has done this since we bought it. I have installed a new pressure regulator hoping it would help with this problem and with the fact that our water hose has low pressure. It didn’t fix either problem. It has been going on for years and I don’t know what to do to fix it. I am on city water and have a gas hot water heater. Any suggestions would be great!

  • Is it only the hot water pressure that is high, or both hot and cold?
    – gnicko
    Commented Feb 2, 2022 at 14:41
  • @gnicko Barring unusual check valves, hot and cold are connected via the water heater, and end up the same.
    – Ecnerwal
    Commented Feb 2, 2022 at 17:16
  • @Ecnerwal I was only seeking clarification. The OP seems to indicate high pressure on the hot side and low pressure on cold. Knowing that it's both (or just hot) is useful information.
    – gnicko
    Commented Feb 2, 2022 at 19:12
  • If you are reading "low pressure on hose" as "low pressure on cold" you are reading more than was actually said.
    – Ecnerwal
    Commented Feb 2, 2022 at 23:29

1 Answer 1


Check the expansion tank, it may have failed or is undersized.

When fresh water gets heated it expands while the backflow preventer causes a spike in pressure in your lines.

  • 2
    Or there isn't one at all; and there needs to be one.
    – Ecnerwal
    Commented Feb 2, 2022 at 13:54
  • Check for a check valve that should not be there. The hot and cold should equalize pressure.
    – Gil
    Commented Feb 2, 2022 at 19:52

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