Hot Water Booster Pump & Bypass Valve System

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by tacker, May 7, 2011.

  1. tacker

    tacker New Member

    Messages:
    7
    Location:
    Sarasota, FL
    I am considering a Grundfos hot-water booster pump and bypass valve to solve the lengthy delay in getting hot water from my water heater to my kitchen sink/dishwasher. This would be a retrofit, so the recommended approach is to have a bypass valve, which recirculates water back via the cold-water lines, instead of an insulated closed-loop hot-water system, which would be difficult or impossible to install in our existing home.

    My questions are:

    1) Do people have experience with this set-up, good or bad?

    2) I am uncertain whether I should be nervous about pressurizing lines with these booster pumps, as regards pinhole leaks in copper lines. In Florida, pinhole leaks seem to be more of a problem than other areas, and I am wondering whether these pumps amplify the risks, either by added pressure on weak spots or by causing further erosion through the system's own action.

    I'd appreciate any useful commentary or suggestions.

    Thanks.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    It isn't a booster pump...it is a circulator. Unless there's a blockage, it doesn't do anything to change the pressure. Plus, it is a quite small pump, and even if it could boost the pressure, it wouldn't be much. Now, because you are moving water more often, it is possible the lifespan of the pipes could decrease, but you might not notice it in your lifetime. If you've got aggressive water, it may make it worse, but if your water quality is normal, probably not.

    You want an engineered solution. There are kits that include the required check-valve and crossover device. If you're looking at a kit, great. If you are trying to engineer it yourself, you may have problems.

    By using the cold water as the return line, you will warm up that leg as well. Depending on the setting of the cross-over control, it may not be a lot.

    I have a system made by Redi-Temp that has been working for me. It's the only one I'm aware of that allows you to set the shutoff point, which can limit how hot the cold line gets (by limiting how hot it must be on the hot side before it shuts off the flow at the cross-over). Others give you what they give you - i.e., it is fixed. I find that if I flush the toilet, that's enough to purge my cold line of the warm water, but then I have the thermostat set fairly low. The unit (it has a built-in cross-over) is under the vanity. The shower is closer to the WH, so it gets hot, while I have warm immediately at the vanity. Other things in the house are generally hot since the line passes them by to get to the cross-over.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,038
    Location:
    Cave Creek, Arizona
    The only downside of the system is that the "bypass" unit WILL fail and require replacement. It is NOT easy, and may be impossible, with a system with it built into the pump. In addition, the best location for the bypass will probably NOT have an electrical outlet for the pump. Grundfos and Laing, for example, have systems with the pump at the water heater and the valve, or valves if necessary, are installed under the appropriate sinks. the flow velocity is fairly low so erosion of the copper is not a problem. Mine has been working for about 8 years with one bypass replacement.
  4. tacker

    tacker New Member

    Messages:
    7
    Location:
    Sarasota, FL
    Thanks, but it is a pump, so it must create a pressure differential, or it could not move water at all and especially across the bypass valve, which faces the cold line under pressure, as well.

    I do appreciate the reference to Redi-temp and will investigate their system, as well.

    Thanks again.
  5. tacker

    tacker New Member

    Messages:
    7
    Location:
    Sarasota, FL
    I'd think replacing the bypass under the sink wouldn't be too difficult. Am I overlooking something?

    Thanks.
  6. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    The differential in pressure would surprise me if it was more then 2psi. I would thing your system could handle that.

    John
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,038
    Location:
    Cave Creek, Arizona
    It does create a pressure differential, but it is NOT enough to stress the piping.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    When the bypass is open, it is a closed loop, and it is just moving the water (fairly slowly) around the loop, not really pressurizing the line. On the redi-temp unit, the pump turns on and off (which will make it wear out sooner, but it could still be many years just like in a heating system); most others leave the pump running constantly, and open and close the bypass as required. The crossover valve on the Redi-temp unit is made of Deldrin, and is rated at over 1M cycles, which is many years - probably more than most others. Mine is now pushing 6-years and the only thing I notice is that the pump is slightly more audible; still works fine, and unless you are listening for it, practically inaudible.
  9. tacker

    tacker New Member

    Messages:
    7
    Location:
    Sarasota, FL
    Thanks to all for comments. Sounds like a "go," and I learned that some of the features of Redy-Temp seem to offer advantages. It costs more, but, maybe, that's worth it.
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