I just got a new 50 gallon water heater and my circulating pump would only keep the hot for 1 shower (progressively getting cooler until completely cold). When I turned off the circulating pump the hot water lasted long enough to take 4+ showers (obviously had to wait a few minutes to get the water hot). I was told by a plumber that circulating pump might be broken (15 years old with no problems), so I bought a new one and exact same issues have continued. Help!!

  • Did you buy the same size pump and could you list the name and model of the pump. and show how it is piped. – d.george Jan 7 at 11:35
  • Sounds like your pump's flow rate is too low for your needs. I would return it and do your research before installing a new one. – MonkeyZeus Jan 7 at 13:54
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    Knowing more about your system would be helpful , the recirculating systems I have installed are only there to provide instant hot water (not having to run the hot tap for several minutes. They use the existing plumbing or a dedicated line) once the water is at temp the recirculating pup shuts down. You may have a different type of system. I do agree with @DDS that the new high efficiency water heaters are slower to recover and may not allow the temp to be set as high as your old one thus causing the problem not the recirculating pump. A point of use electric may be needed. – Ed Beal Jan 7 at 15:30

Rise boiler temperature to over 60°C, also ensure that the recirculation pump does not run too fast (or your hot water mains will act as crawlspace heaters). The other option could be that your new boiler is slower to recover: the heat-pump kind is more energy efficient but really slower to recover.

You could address it by setting higer temperature on the boiler (colder return water will mix with hotter water in the tank keeping the temperature correct)

Install an 'on call' recirculation: it starts when you switch on the light in the bathroom. Other option is with a flussostat: you open hot water for few seconds (then close it and wait a minute), pump kicks in bringing hot water to the taps, you open the faucet again and have hot water without having to keep the pump costantly running.

A simplification could be turning on the pump at specific times (in the morning and in the evening) so the tank during the day has only to heat itself and not the whole circuit.

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