We had a Rheem 50 gal 12 yr gas hot water tank for 6 years with no issues. We started having an issue around Dec where the water was cooling during a shower. The same coolness was in other faucets and showers. We replaced it with the same new tank a month later and found the same issue. There is no leaking, no change to shower pressure, no new building, same amount of people. No change to anything to do with our gas. The only thing that’s out of the ordinary, was that we had our gas furnace serviced shortly before the issue started.

Why do we not have enough hot water?

Would love to hear from someone.

Thanks for your time

  • 2
    who replaced it, did you ask them? equipment and installation should have warranty. There are many reasons, and if you didn't do the work yourself it will be hard to diagnose and fix over the internet
    – P2000
    Jan 19, 2023 at 4:16
  • 1
    One solution might be to turn up the set point on the WH and have a plumber add a mixing valve to ensure the hot water delivered isn't dangerous ......DK why this problem appeared, but this is a possible fix. Jan 19, 2023 at 10:12
  • 1
    In servicing the furnace, they may have changed a setting on a gas valve somewhere that's impacting the water heater's ability to provide heat. However, as you've written this, it isn't really a question, (take the tour - this is a Question & Answer board), but an invitation for discussion (which this site is definitely not for). Please edit to ask an explicit question that we can provide an actual answer for.
    – FreeMan
    Jan 19, 2023 at 12:13
  • @FreeMan....fixed it.
    – RMDman
    Jan 19, 2023 at 13:21
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    When the problem happens, are you able to get how water at other locations - e.g., kitchen faucet? If so, the problem has nothing to do with the water heater and instead may be a problem with the plumbing in the shower. In particular, many places now have anti-scalding mixing valves, which are an important safety feature but if they fail (and fail "safe", which is actually a good thing) the result can be cold water coming out. Jan 19, 2023 at 15:21

2 Answers 2


If you have an older home with cast iron pipes your gas line could have blockage in it or breakdown of the inside of your gas pipe line could be causing particle build up in your devices.

IF your water heater is not getting a good flow of gas and therefore is not producing a good flame, it will be limited on how hot it can get the water.

This might be especially true if the reason you had your furnace serviced is because it wasn't working efficiently and the service tech had to clean out particles in the furnace tubes.

You can have a company come out and inspect your gas lines. They can test the pressure and see if you have a leak somewhere, maybe it is outside and so you are not smelling the mercaptan (smells like rotten eggs) added to the gas to let you detect, through your sense of smell, that you have a leak.

You should check with your gas company to see if they did some repairs to their lines lately that could have knocked debris loose or be creating a low flow.

A higher than normal gas bill can indicate a leak.

If you have a gas stove and you cannot get the flame up as high as you use to, that could be an indication that a blockage could be located on your main line before the stove or low flow due to leakage.

Good luck! Hope this helps at least narrow down the mystery!

  • 1
    An edit to improve formatting to break this down from one giant paragraph would help make it more readable. Otherwise, it seems like some pretty good suggestions.
    – FreeMan
    Jan 19, 2023 at 19:00

First idea: the service technician lowered the thermostat setting (just turn it to 60°C or hotter, otherweise hot water will just not less).

Another idea is that the hot "delivery" pipe, if your tank is wall-mounted "pipes from below" Or the cold "injection" pipe if your is floor type "pipes from above". (note: the longest pipe inside the tank)

Is corroded mid-heigt it causes cold water to be injected mid-height instead of at bottom (or, vice versa, hot water being sucked at the bottom) disrupting the stratification.

Both resulting in percived reduction of boiler capacity (but not causing leakage being those pipe inside the boiler. But this second scenario shouldn't happen with a new boiler.

  • Are you referring to the "dip tube"? That would make sense up to the point of installing a new tank...
    – gnicko
    Jan 20, 2023 at 14:36
  • Yes, I just didn't know its name in English
    – DDS
    Jan 20, 2023 at 15:44

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