Drain Water Heat Recovery supply loss help

Discussion in 'General Plumbing Help' started by Andrew R, Jul 10, 2019.

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  1. Jul 10, 2019 #1

    Andrew R

    Andrew R

    Andrew R

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    Hello I have a newly built home that came with a DWHR pipe. The home is fairly large and has alot of plumbing. 3/4 " supply's most of the initial runs and eventually they branch 1/2" PEX.

    My question today is regarding supply problems. If I run 2 things at once (both 1/2" outlets)e.g a bath and a garden hose simultaneously the GPM on them becomes painfully bad.

    One thing in perticular that is catching my eye is how everything (hot &cold ) is first piped through a drain water heat recovery unit. 30ft of 3/4" to the unit and then 30ft to the hot water tank or out to other cold outlets. The DWHR says on it 1.9 psi loss. But what about all this extra length of piping? Could this silly unit be killing my supply?

    Please help.
     
  2. Jul 10, 2019 #2

    Diehard

    Diehard

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    Are you saying that ALL the water used in the house, including the garden hose, is flowing through the heat recovery unit first? That doesn't make any sense at all.
    Well it's telling us it's killing 1.9 psi of pressure but that based on a particular flow rate. Now I'm not familiar with these devices but I suspect that the 1.9 psi pressure loss is based on a typical hot water use flow rate, which would be much less than what it is actually seeing. In other words, you're losing a lot more pressure than 1.9 psi when you exceed the flow that 1.9 psi loss was based on.
    And of course, you are also unnecessarily losing more pressure through any common line feeding that unit if it's for a cold water demand and should have a separate line.
     
  3. Jul 10, 2019 #3

    Diehard

    Diehard

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    Out of curiosity...
    Is you 3/4" lines PEX also?
    Is the heat recovery unit made up of all copper?
    Does it have a manufacturers name and model?
     
  4. Jul 10, 2019 #4

    Andrew R

    Andrew R

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    Power-pipe R3-48
     
  5. Jul 10, 2019 #5

    CT18

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    What is the current psi in the house with nothing flowing
     
  6. Jul 10, 2019 #6

    Diehard

    Diehard

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    The best I can determine, without reaching the manufacturer, is it looks like the testing criteria may have been up to 3.79 gpm.
    So, of course, if you were to say double that flow rate, that would like quadruple the head loss.
    (If you do check your water pressure when it's not flowing(static pressure), you should plan on checking it flowing, both the service and at or near the point of use, at a particulate flow rate, if want want to get some meaningful info.)
     
    Last edited: Jul 11, 2019
  7. Jul 11, 2019 #7

    Matt30

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    Those DWHRs are an absolute cash grab. They don’t work. The only reason they are installed here is because they get your home a better energy efficiency rating just by having them.

    If all the water throughout the house flows through this thing, then that is even worse. It should just be the cold water supply to the water heater.
     
  8. Jul 11, 2019 #8

    Diehard

    Diehard

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    It's a newly built house.? If you have plumbing inspectors up there, I would question them on it. Maybe you have some recourse, to get the plumber to fix the error.

    Although I have no personal experience with these units, all the reviews I read on them were quite favorable.

    EDIT: In any case, one way or another, you have to limit the water going through that unit to the water feeding the water heater only. All cold water demands should be taken off upstream of the unit.

    Do you even have a hose bib or somewhere you can hook up a pressure gauge upstream of that unit?
     
    Last edited: Jul 11, 2019
  9. Jul 11, 2019 #9

    Andrew R

    Andrew R

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    I have re piped my water supply in the basement removing the DWHR from use. Thanks for the info. My GPM while running multiple outlets has definately improved.
     
  10. Jul 11, 2019 #10

    Diehard

    Diehard

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