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Community and Q&A

Grundfos w/ Timer or Grundfos Adapt

saltarch | Posted in Mechanicals on

Considering the Grundfos w/ Timer or the Grundfos AutoAdapt recirculation pumps for a new house and hoping someone had experience/ feedback with either or both. 


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  1. utah_matt | | #1

    Bumping this thread. My plumber told me today that he installs Grundfos Adapt.

    I had grand plans on installing perfect plumbing runs but this fight wasn’t worth it to me so I will go with what my plumber recommends. Unless, this great forum recommends a different solution that won’t greatly offend my plumber.

  2. greenright | | #2

    Neither. Install a dumb recirc pump and plug it into a tplink kasa smart plug. Then create an Alexa routine to turn on pump for say 5 mins with “Alexa hot water” phrase or similar. Works well, saves the largest amount of hot water and house tenants get used to calling for hot water easily.

    Any smart automation will waste about 1/4 if your hot water. Manual call as described above is the most efficient recirc strategy. I have tried them all.

  3. Expert Member
    Akos | | #3

    The one that definately is annoying is the timer. These tend to drift plus add in the occasional power outage and you have to fuss with them.

    The adapt version does have the benefit if set it and forget it.

    For me, the one that works the best is a motion sensor in each bath. No need to adjust anything, always guaranteed to work. It does mean a bit more wiring.

    1. Jason_K | | #4

      Akos, is there a specific pump you recommend for this? I'm looking for a pump that has an aquastat that can be plugged into a receptacle wired to a motion sensor in the bath like you suggest -- just want it to not run if the line is already hot. So far, closest I've found is the Grundfos ALPHA 15-55 HWR-T, but I don't love the thought of the bluetooth sensor and don't know how well that would handle being plugged into a switched outlet.

      1. Expert Member
        Akos | | #5

        I think if you look at the runtime with a motion sensor, you are probably saving pennies by adding in the aquastat. I wouldn't bother, keep it simple.

        I would get a slightly larger pump with a motion sensor to avoid delays. My 4.5gpm one is a bit too small. A Taco 006e3 would be better, plus it can be turned down if the extra flowrate is not needed.

        P.S. For the OP. You can also add a relay module (ie RIBU1C) in parallel with the pump signal. The coil outputs of the relay module can be used to trigger your ERV/HRV boost or to drive a bathroom fan.

  4. saltarch | | #6

    Thanks for all of the feedback. I spoke to our plumber a bit more as well. He has installed several of the Grundfos w/ digital timer and had success.

    To me it feels like it checks the most boxes. Not overly technical, easy to setup and control. Also, 95% of our hot water usage is in the morning and evening, so the timer allows for dialing in on the majority of usage with little effort.

    Motion sensor is a good option, but additional switching and wiring. Also, there a lots of times people are in and out of the bathroom and don't need hot water.

    Alexa and push button timers require user input. How often are my kids going to actually do that...or guests.

    1. Expert Member
      Akos | | #7

      If you are on city water, one simple add on is to serpentine the return line under the bathroom floor before running it back to the recirc pump. You can put heat spreaders on them (Ultrafin works great for this) and now you have a simple low cost floor heat. You can just see the first heat spreader in the picture. For a reasonable sized bathroom, you only add maybe an extra 25' or so of pipe. Make sure to insulate bellow pipes and block off the joist bays outside the bathroom to contain the heat.

      In the winter time you can run the recirc all the time to get the floor even warmer. In the summer, leave it on the timer. Since it is potable water you want to make sure the water in there doesn't stagnate, so the recirc should run daily for at least 15min. It does add a bit of extra summer cooling load, but warm floors in the bathroom are a great thing even in the summer.

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