Water recirculating pump problem

By June 19, 2016 Plumbing, Problem Solving
grundfus pump

Estimated reading time: 1 minute, 52 seconds

grundfus pump

Grundfus pump

Stump the Plumber

This is another installment in the stump the plumber series.

The situation

I went to look at a kitchen remodeling project and during my evaluation I asked an open question that I always like to explore. “Is there anything else that you would like to discuss, or anything not working?”

They responded that they had a plumber install a Grundfos comfort system (recirculating pump with a timer) that was supposed to have hot water at the sink, but it had never worked.

I figured that they do fail occasionally but I had never had one not work right out of the box.

Naturally I had a look and sure enough “The Plumber”, likely a family friend had but it on the COLD side and set the instructions on top of the gas water heater near the flu.

The only other way to make a mistake would have been to install it upside down.

I laughed when I thought of how hard the pump had been working all these years pumping water back out into the city water system.

The solution

Other than the instructions had nearly caught on fire, sitting atop the gas water heater, switching the unit to the proper HOT side made a world of difference.

We are men. Instructions are for sissies, right? I call them “distructions” (a combination of directions & instructions) Who knew they had important information in them?

I felt like I had pulled a thorn from the lions paw. Odds are we will be friends for life!

What is all this about recirculating pumps

Recirculating pumps are great, I use one at my home. They recirculate hot water through the system in a continuous loop when you set the timer properly decreasing the amount of wasted water waiting for the hot water to show up.

Here is a link to another post about them.

If you or someone you know could potentially use our services, or just wants to speak to a trustworthy contractor please contact me, you’ll be glad you did.

Your comments are welcome. To ask questions or get more information about proactive residential care, click here to email me directly, or call 208-639-1808


  • jahn Maran says:

    I have installed a watts recirculating water pump and cannot get to work. It is not the temp sensing unit under the sink since this has already been replaced. I contacted watts and their reply is that this sometimes happens and they have no idea why? Then I contacted Grundfos and received pretty much the same response. The pump is installed correctly and I can hear the motor humming so I know the electrical connection is ok. Can you give me help

  • Dean says:


    MY 9-year- old Grundfos hot water recirculating pump suddenly quit sending hot water to the farthest hot water faucet. The pump is installed correctly and the lines into and out of the pump are both hot. So I think the problem is not with the pump. I checked online, and am guessing I need a new bypass valve. Troubleshooting instructions I found online said to turn off the cold valve at the angle vale under the sink and then open the cold side of the faucet and then when the water slows to a trickle, check to see if it is hot–hotter than 90 degrees. I did that, and the water trickle is cold, Do I need a new bypass valve?

    • joe says:

      Dean, the line in and out of the pump will always be hot if it works or not because that is the route the water takes. Make sure the timer is set correctly, several power outages could make the schedule screw up. Can you hear the pump working when it is supposed to be circulating? If you take the pump out and turn it on it will work or not. The bi-metal part under your sink has no moving parts and would be an unlikely culprit. When the pump should be coming on, say in the morning after resting at night, you should be able to sense that warm water is going back in the cold line so your sold faucet should produce warm water for a little bit. (You have probably noticed that over the years) if it is not behaving in that way you likely have a failed pump, hate to say it. Not sure if they are repairable, What is the life expectancy? I have no idea. I have never replaced one. 9 years? certainly out of warranty. Let me know what you figure out. Joe

  • John says:

    I have a Bell & Gossett recirculation pump and I have to tap it with a hammer to get it to actually start pumping after the aquastat shuts it down. Otherwise it just hits and gets hot.

    • joe says:

      Sounds like the motor needs to be separated from the pump and taken to an electric motor shop for repair / rebuild or worst case, replaced with a new one of the exact same. Not sure if you are doing it yourself. I would think an electrician would be the most helpful in this situation rather than a plumber. From your description it seems like the pump portion is fine. You can always opt to have a plumber help to replace the entire thing. Then you would have a spare to rebuild and have as a backup. Best of luck. Joe

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