Can my new tankless water heater work with my existing hot water recirculating system?

Asked by george johnson
Oxnard, CA

I have a pump and the loop is currently run off a standard water heater outlet. The tankless is a Takai unit.


Raymond Pruban

Answered by Raymond Pruban

Woodbury, MN

Amaris Custom Homes

December 28, 2010

Generally it is not a good idea to have a hot water recirculating system that runs 24/7 with a tankless water heater.

  • The problem is the tankless water heater will keep cycling on and off, thereby defeating the purpose of the tankless water heater, which is to save energy.
  • Also, I have heard that some tankless water heater manufacturers will void the warranty when the tankless water heater is connected to a recirculating pump.

The other problem you might run into is the flow rate of the recirculating pump may not even turn on the tankless water heater.

  • Grundfos does make a recirculating pump for tankless water heaters, but you need to make sure the two devices will work together.
  • Navian makes a tankless water heater with recirculating pump built in.

Use a timer or on/off switch

To configure this system with a tankless water heater, it is best to use a recirculating pump that is on an automatic timer or on a manual on/off switch at the point of use.

  • If it is on a timer, ideally the timer would only run the recirculating pump for say 1-2 hours in the morning each day and be off the rest of the time.
  • If on a manual point-of-use switch, when you get up in the morning you turn the switch on and then turn it off after your showers are done.

The biggest knock against many tankless water heaters is that the water takes a while to heat up and a lot of good clean domestic drinking water goes down the drain. The benefit of a hot water recirculating system will be to save water.


For more information:

Read Harold Remlinger's Q&A "Can I use a closed-loop hot water system with a tankless system to minimize water wasted when a faucet is opened?"

Tagged In: tankless, hot water recirculating

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