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Thread: Hot water recirculation loop size?

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  1. #1
    Water system engineer riverside67's Avatar
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    Default Hot water recirculation loop size?

    What size should a dedicated hot water recirculation loop line be to be effective?

    Does the size of this line add to the volume capability of the main hot water feed line?

    Does it need to be the same size as the main hot water feed line?

    Thanks

  2. #2
    Plumbing Designer FloridaOrange's Avatar
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    1. That would depend on the size of the system and the length of the hot system.
    2. No, because it is the return to feed the water heater.
    3. No, but in some instances it can be.

    For a typical system a 1/2" recirc line does the job.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  3. #3
    Water system engineer riverside67's Avatar
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    The length of the hot water system would be about 100' from the heaters to the furthest faucet/bathroom and about 100' back, total ~ 200' return line I'm presuming. I'm planning on having an 1.5" hot and cold water main trunk line ran from the heaters to the furthest bathrooms since both will have high performance type showers.

    We will have a 2" feed line coming into the home from our well.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The pumps in the recirculation systems I've looked at are designed for 1/2" lines, so I don't think you'd gain any benefit of a larger return line. Make sure you insulate those supply lines very well, or you'll be wasting a huge amount of heat with them acting as big radiators.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Water system engineer riverside67's Avatar
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    jadnashua,

    Won't the supply lines be ran underneath my slab?

    How are the copper lines properly insulated under a slab?

    You are speaking of just the hot water supply correct?

    Does the hot water return need to be insulated also?

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    A very large hot water pipe in contact with the soil underneath the slab without insulation will waste a huge amount of energy. No easy way to tell if they are insulated now, but you might see something as it comes up through the slab. the lines could be anywhere in the house or attic.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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