I have Rheem water heater and newly installed circulation pump. I am facing a weird situation with the circulation pump which is that the circulation pump is set to run between(4PM-9PM). When I take shower in the bathroom upstairs, at 10 PM. the water is barely lukewarm. However, when I take shower when pump is on, the water is hot.

I do expect the water to be hot enough after the circulation pump is off. This is because I expect that water has been heating up for 5 hours, there may be some cold water in pipes but once that water runs out, I should be receiving the hot water from the heater directly. I was in the shower for 20 minutes and I received lukewarm water for all 20 minutes.

Am I having the wrong expectation here?

  • how far is it from the water heater to the shower head? is it a tankless heater? if you run the shower at 10PM does the outlet pipe of the heater get hot?
    – Jasen
    Jan 9, 2021 at 19:50
  • @Jasenwater heater is indeed far from the bathroom and it is a gas water heater with a tank. I have not checked the pipe being hot at 10 PM. I can get that answer soon.
    – Lost
    Jan 10, 2021 at 17:13

1 Answer 1


Your expectation is correct, once the warm water is flushed you should then have hot. There are 2 types of recirculating systems one one uses the cold line and has the pump and check valve (I believe this is the type you have) in a recirculating system on the cold line if the check valve fails it ends up being a mixing system. A 3 line system has a separate line the hot is recirculated on the second line so it would not be long even with a failure until all the water in both lines was hot.

So check your pump system as I believe the valve is allowing the hot to mix with the cold while in use and that should not happen.

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