Recirculating Pump or Point of Use tank?

Discussion in 'General Plumbing Help' started by bowens, Jun 6, 2019.

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  1. Jun 6, 2019 #1

    bowens

    bowens

    bowens

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    Hi, I just bought my first house (east bay of San Francisco) which had a gas water heater located in the interior of the house. It failed, and I opted to have it replaced with a hybrid (in anticipation of solar) and installed it in the garage. Of course, now it takes a while for the hot water to show up at the kitchen sink, about twice as long as before (and this will only get worse when it's the cold season).

    I'm trying to decide between installing a recirculating pump vs a point of use device (like a 2.5g tank). What I'm understanding about the pump is that it will be maintaining a temp in the pipe 100% of the time, so I'm leaning towards going with the tank.

    Install with a Point of Use tank is quite a bit less, but it will only remedy the situation at the kitchen faucet. The pump method will address the whole house, but then there's the heat loss issue. The house is raised, so access for either is not much of an issue.

    Is there anything I'm missing, and is there a way to better compare the two types of systems rather than going on my hunch?

    thx,

    brad
     
  2. Jun 6, 2019 #2

    RenewDave

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    The tank is a bad idea. If that tank stops working you have to push that 2.5 gallons that is cold through before you get hot water. And you end up with a sandwich effect. A recirc system gives you more bang for your buck and a grundfos retro recirc system you can set up in a couple of hours and be done. The average family wastes between 11 and 16 thousand gallons of water a year, waiting for hot water.
     
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  3. Jun 6, 2019 #3

    bowens

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    sandwich effect? is that in the non-working scenario?
     
  4. Jun 6, 2019 #4

    Diehard

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    Keep in mind that a recirc system can be set up in a number of different ways. For example, it can be arranged to start recirculating based on a timer, a manual switch, a temperature sensor on the return line that would shut pump off when satisfied and better still, a combination of the above control parameters. Whatever one feels best suits there needs.
    Of course insulating piping is a big plus.

    Although simpler to set up, I am not a big fan of the types that use the existing cold water lines for the recirculation. It allows an amount of water that has passed through the water heater to mix with the potable cold water. I consider water that has passed through a water heater has added contaminates and is not a good idea to use it for human consumption. Although many people do, in one way or another.
     
  5. Jun 6, 2019 #5

    Mikey

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    ...but it's also been heated (in my case to 160°), so it might have less bacterial contamination than the cold side.
     
  6. Jun 6, 2019 #6

    bowens

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    well, I'm gonna go with a PoU tank. I just can't get past storing hot water in a long copper pipe, even if the heat loss is mitigated by insulating & timing.
     
  7. Jun 6, 2019 #7

    frodo

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    POU tank is a good option
    holler back if you need help plumbing it

    do you know which unit you will use?
     
  8. Jun 6, 2019 #8

    bowens

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  9. Jun 7, 2019 #9

    frodo

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    little guy aint it

    you are aware that is only 2.5 gallons right?

    • from the link
    • For low-demand Point-of-Use applications, such as a hand washing sink
     
  10. Jun 7, 2019 #10

    bowens

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    the way it was explained to me by one of the PoU manufacturers I called prior is that the small tank will provide hot water until the hot from the main tank arrives, which is a little over one gallon's worth. Not sure what the setup is, but that's how it was explained to me.
     
  11. Jun 7, 2019 #11

    frodo

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    so let me get this in my head.
    you do not want a circ pipe from the water heater to the sink
    because
    it is important not to waste energy

    so in order to not waste the energy of the heat loss in a 3/4 line.
    you are installing a pou heater under the counter that will cycle on and off all day keeping the water at the ready?

    I have a much much better idea that will conserve electricity and water and give you instant hot water
    interested?
     
    Last edited: Jun 7, 2019
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  12. Jun 7, 2019 #12

    bowens

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    of course, I'm interested!

    That is the tradeoff, as you note--stored hot water in a pipe vs. in a tank. Less surface area in a tank, so I went that way. Also, it will be solar powered, at least when the solar is generating; I notice that the hybrid tank cycles very little when there's no demand, so I expect similar for the PoU tank.
     
  13. Jun 7, 2019 #13

    frodo

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    install the circ line and pump
    control the pump, from the light switch that turns the light on over the kitchen sink
    if your house is like most houses you have an overhead light above the sink
    run a wire from that switch back to the pump
    when you walk into the kitchen and turn on the light, the pump kicks on
    and shoots hot water to your sink. by the time you reach down and turn on the faucet, the hot water is there.
    no heating the pou water all day
    no wasted energy or heat loss in the circ line
    no wasted water running down the drain waiting on it to get hot
    [​IMG]
     
  14. Jun 7, 2019 #14

    frodo

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    also
    this can be expanded to a bathroom, using the same principle
    you would need to install 3 way switches and a runner wire from kitchen to bathroom

    think. 3 way switch in your hall
    on one end of the hall is a switch that turns on/off the light
    on the other end is a switch that also turns on off the same light

    same thing
     
  15. Jun 7, 2019 #15

    bowens

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    thanks, but I think I like the more integrated approach with the tank, as well as simplicity and cost of installation. The tank won't be much of an investment, so I can see how it goes with that for now.
     
  16. Jun 7, 2019 #16

    frodo

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    ok . holler if you need help or have any good recipes to hand out
     
  17. Jun 7, 2019 #17

    bowens

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    I appreciate the responses!
     
  18. Jun 7, 2019 #18

    Diehard

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    Yes that makes sense. It's being fed by a hot water system so that it's effective capacity(while being fed initially with cold water) only needs to match he capacity of the hot water piping.
     
  19. Jun 7, 2019 #19

    RenewDave

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    Sorry, been away. The sandwich effect is where you have two heated tanks and a length of pipe in between. The length in between gets cold and then it moves into the second tank when you use water. You’re hoping that the 2.5 will have enough storage AND heat the cooled length of pipe water until the big tank gets there.
    The energy loss/use issue seems like a non-issue. You’re paying to heat water 24/7 whether in a tank or in a copper line.

    https://www.amazon.com/Watts-500800-Instant-Recirculating-Install/dp/B000E78XHG
     
  20. Jun 7, 2019 #20

    frodo

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    correct superDave
    what happens is his wife starts doing dishes with hot water then the water goes cold
    then heats up again.
    no yum yum at midnight for hubby
     

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