Our two-story-on-a-slab house has uninsulated copper pipes, including a recirculation return pipe to a tee on the water heater drain. In past years, the recirculation seemed to give us hot water fairly well (though at an energy cost), but less well of late. We recently changed out the hot water heater, and replumbed the recirculation system because of physical differences. We found that the return check valve was stuck open by calcium deposits, and the aquastat was not even connected. We have added a timer for the recirculation. The existing pump is a Grundfos UP 15-42 SF (59896171). AC power to the pump measures 75 watts and 75 VA. A water pressure gauge on a tee at the water heater drain measures a rise of 5 psi when the pump runs, so seems to say that the pump works. But, we find that even after letting the pump run for an hour, there is no detectable heat on the return pipe, and no hot water available at faucets. Where do we start in getting this to work properly?

P.S. We also have a Chilipepper demand pump in the master bedroom bath, farthest from the water heater, and it works great (crossover hot to cold until temp rises); but wife objects to the noise, and would like the timed recirc to work.

old photo - http://smg.photobucket.com/user/acellier/media/Recirculation/2014%2010%2017%20old%20water%20heater.jpg.html new photo - http://smg.photobucket.com/user/acellier/media/Recirculation/2015%2003%2011%20installation.jpg.html

A thought - could the heater possibly have a check valve on the drain???

  • Make your "problem solved" into an answer, and I'll upvote it and the question :) Mar 12, 2015 at 22:00
  • Thanks for the follow-up! One more thing, by the way: Photobucket ate your pics, so you'll have to repost them if you want them to show up in your post. Jan 23, 2020 at 3:59

1 Answer 1


D'oh - Problem solved. Heater drain valve was not opened sufficiently, due to unfamiliarity with the new-style plastic collar-operated drain valve. The key clue was the rise in indicated pressure, which showed that there was impedance into the tank. With the valve correctly opened, there is no rise.

  • Huzzah! Glad you were able to figure this out! Jan 23, 2020 at 3:47

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