I have a dedicated 1/2" recirculation line back to the water heater tank via a tee at the drain valve. I've purchased a new pump (Grundfos UP 15-29) to replace original 15yo. There's a check valve located just upstream of this pump. However, I've seen drawings with the check valve downstream of the pump & upstream of the tee to drain line. Does it matter whether located u/s or d/s of pump? Also, would a "spring" type check valve be preferable vs flapper check valve? Within the recirc line, there's two zones, however, the zone furthest from heater takes over a minute for hot water to faucet. Thinking of installing a valve on the shorter line to throttle back for more uniform circulation to both zones. Is a ball valve OK or recommend other type of valve?


1 Answer 1


The pump you purchased is way oversized for the application.Instead of the "UP 15-29" pump you should have purchased a UP 10 or a UP 15-10, the smallest pumps they have. Make sure the pumps are made of bronze or stainless steel. Iron or steel pumps should not be used on domestic water. The UP 15-29 moves too much water and may "wipe the elbows" (wear out or wear through) due to the high flow rate. You only need a very low flow rate to insure almost instant hot water flow at the faucets. I have 3 zones for the 3 bathrooms in my home. A check valve at the take off tee for each dedicated return line is imperative to stop "back flow" from the other dedicated returns. I would not use spring checks and use only angle checks due to required head needed to lift the spring checks. I would also install a timer to run the pump only during the day when your household is awake. No need to run the pump when everyone is asleep. continuous running pumps are only used in hospitals and large commercial buildings due to their constant hot water use.

  • I thought that the UP 15-29 is the replacement pump for the UP 15-18 (which is actually the model # of existing pump. So the location of the current check valve, just upstream of the pump is correct?
    – Grant
    Apr 13, 2017 at 15:53
  • It may be an exact replacement but you don't need to move that much water. My pump is a B&G NBF-8S rated at a max 7 GPM. and 8 feet head which is more pump than I need. No reason to have a larger pump than needed.
    – d.george
    Apr 13, 2017 at 20:42
  • Per Grundfos, when a check valve inline, the flow curve drops from 20 GPM to 13 GPM at zero head. Although more flow than needed, 0.74 A load not a big deal in terms of wasted energy. Comparable to a 75 W light bulb. Still looking for feedback whether needing a valve to throttle down one of the zones.
    – Grant
    Apr 16, 2017 at 15:53
  • My 3 zones are all different lengths from the hot water tank and circulating pump, and all get hot water in about 30-45 seconds after the timer starts the pump in the morning. All 3 have 1/2" ball valves for isolation and all valves are all wide open with no need to throttle any of them. When I turn on the hot water faucet I get hot water in 2-3 seconds.
    – d.george
    Apr 17, 2017 at 10:58
  • I do not under stand your statement that it takes over a minute to get hot water when the faucet is opened. if the pump is running you should get hot water right away, unless that zone is blocked or not working.
    – d.george
    Apr 17, 2017 at 11:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.