Replaced a 20+ year old natural gas 75 gallon water heater recently with an equivalent model. The plumber said an expansion tank was required per code. Two things I’m noticing now with the new set up:

1) Low hot water pressure: I used to turn hot and cold on full to fill a bathtub. Now, if I turn them both on full only cold water comes out. I have to turn the cold to half and hot to full to get a decent flow.

2) Two people took baths at the same time (one a whirlpool) and we ran out of hot water for the first time ever.

Is this because newer equipment (same specs on paper) isn’t as good as old equipment? Does the expansion tank explain any of this?

  • Did you ever get this resolved? If so, please give a check-mark to the answer or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
    – FreeMan
    Aug 17, 2020 at 17:29
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    I’m voting to close this question because it's been abandoned.
    – FreeMan
    Dec 15, 2020 at 19:18

1 Answer 1


The new tank may have been piped wrong, and restriction may have been introduced. Did the plumber reduce the pipe sizes in and out of the tank. The new tank will supply the same amount of hot water as the tank you re[laced. The expansion tank is not the problem. Something has changed, you have to find out what.

  • The thermostat(s) probably just turned down. Dec 11, 2021 at 3:59
  • Check and be sure the valves are fully open. Check and validate they did not do anything to restrict the water flow.
    – Gil
    Apr 10 at 0:40

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