Do hot water recirculation systems work? What kind would you recommend?

Asked by Mei Lie Wong, Santa Clara, CA

I've seen advertisements claiming that hot water return systems will recirculate your water until it is the correct temperature, so that the water comes out hot when you turn the tap. How well do these systems work? Are they energy efficient? There are both active and passive systems. Which kind do you recommend?


Kevin Burrell

Answered by Kevin Burrell

Sausalito, CA

Kiwi Plumbing

April 19, 2007

I prefer passive hot water return systems to active recirculators.  

Passive hot water recirculation systems work well and are energy efficient; they can cost approximately $500 to $700, including installation. 

There are two different types of passive systems.

  • One is the Grundfos Comfort Series, which involves an electric pump that is placed on the hot water heater outlet, pressurizing your hot water system to 3 to 4 psi (pounds per square inch).
  • The Grundfos system enables you to install a bypass valve at remote locations where necessary (at the kitchen or vanity sink, for example). The bypass valve bleeds some hot water into the cold water system periodically to maintain the hot water at a level that most customers would be happy with. The benefit to this system is that it can be retrofitted after the sheetrock is up. The downside is that some people notice that their cold water initially can come out a little warm.
  • The other type of passive hot water recirculation system on the market requires small pumps to be placed directly at the remote locations instead of at the main hot water heater outlet. The drawback to this system is that you need an electrical power outlet near each pump, which can be a problem in a retrofit application.
  • One manufacturer of this system is Laing Thermotech, Inc.

An active hot water return system is a hot water line that runs throughout the house and then returns back to the water heater, with a pump on it.

  • This type of system is more expensive, at $1,200–1,500 for the unit and installation.
  • To run such a system continuously would be very energy inefficient.
  • If you choose this type of system, you will want it to run on a timer and you should make sure pipes are well-insulated to avoid heat loss.


For more information:

Check our hot water recirculating Q&A to see what questions other homeowners are asking about these systems.

Tagged In: green plumbing, hot water recirculating

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