I currently have the Watts Recirculating system, pump Model 500803, on my water heater with the bypass sensors located under two areas in the house. We have enjoyed it. The con on this is that the cold water now takes too much time to make it to the spigot due to the lag time for the sensor to stop the reverse flow. We are doing a remodel and I am now running a dedicated line back to the water heater from the the farthest spigot and will remove the under sink bypass sensors making it a closed system now. I was told to purchase a new pump, Grundfos Type UP15-10B5, for the return line to be mounted on the water heater cleanout spout as per instructions. Rather than spend the money on a new Groudouf pump, could I just leave the Watts pump on top of the water heater? Or move the Watts down to the spigot area. Both pumps look familiar and have same flow direction. No photo description available.

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1 Answer 1


I believe that you could use that pump as you describe pumping through a dedicated return line. For reference, this is what I did for my house. I have 3 bathrooms, so I ran a 1/2" dedicated return line from each bathroom to a point near the hot water tank. At that point, I tied all the lines together and ran that line thru the smallest bronze pump I could buy that was for domestic water. On the discharge of the pump I installed a 1/4" orfice to limit the pumps flow and from there to the bottom of the tank. I use a timer to only run the pump at specific times. This set up has worked for 20+ years. One last thing, When running the dedicated line, make sure that you install an isolation valve and a check valve to stop any reverse flow.

  • I agree why you would need a different pump is beyond me it is doing the same thing circulating the water from point a to b. I like dedicated returns, a tiny additional cost up front but lower long term cost as you now don’t have to dump hot water to get the cold out of the tap. +
    – Ed Beal
    Jun 10, 2019 at 14:11

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