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Thread: Where to connect hot water recirculation line at water heater?

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    DIY Member gplumb's Avatar
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    Smile Where to connect hot water recirculation line at water heater?

    I am installing a hot water recirculation system with a dedicated return line and a circulation pump at the water heater. There are two options for connecting the return line - the bottom of the water heater tank at the drain or to the cold water inlet at the top. I realize that unscrewing the drain hose bib can be a problem if it doesn't come out easily,i.e., it's only plastic and can break. If the connection is to the inlet, then an additional check valve is needed to prevent recirculation line hot water from feeding the cold lines when there is cold water demand in the house. What are the trade-offs?

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    Master Plumber master plumber mark's Avatar
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    Talking its better on top

    I think its better on top because the dip tube will
    circulate and stratify the returning water equally throughout
    the middle of the tank instead of being put back in at
    the very bottom....

    comming in at the bottom of the heater also gives the
    heater a false reading and probably makes it turn on more often...
    (that is my theory)


    either way you still need a check valve on the incomming coldline...

  3. #3
    In the Trades GoTanklessToday's Avatar
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    Quote Originally Posted by master plumber mark
    I think its better on top because the dip tube will
    circulate and stratify the returning water equally throughout
    the middle of the tank instead of being put back in at
    the very bottom....

    comming in at the bottom of the heater also gives the
    heater a false reading and probably makes it turn on more often...
    (that is my theory)


    either way you still need a check valve on the incomming coldline...

    Concur.

    Make sure you install a boiler drain before it enters the heater to purge the air. We go shutoff, pump, boiler drain, shutoff, into tank.

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    Plumbing Contractor srdenny's Avatar
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    "comming in at the bottom of the heater also gives the
    heater a false reading and probably makes it turn on more often..."
    If the return line is properly insulated, the ∆T will not be so great as to confuse the thermostat. Plus, sending it back into the bottom of the tank stirs the water at the tanks bottom and helps prevent sediment buildup down by the burner...
    and that's my theory.

  5. #5
    In the Trades GoTanklessToday's Avatar
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    Quote Originally Posted by srdenny
    "comming in at the bottom of the heater also gives the
    heater a false reading and probably makes it turn on more often..."
    If the return line is properly insulated, the ∆T will not be so great as to confuse the thermostat. Plus, sending it back into the bottom of the tank stirs the water at the tanks bottom and helps prevent sediment buildup down by the burner...
    and that's my theory.

    I wouldn't say that either way is the right way, I've seen it done both ways equally. The reason we would prefer it to go down the dip tube is that if its done right, you don't have to do any re-work when the heater is replaced in the future. Also, removing the drain valve and altering the "as manufactured" configuration, you are technically decertifying the UL or AGA rating. This "technically" voids the warranty.

    If I lived in a hard water area, I may consider the drain valve way more for the reasons you mentioned though. Keep the "junk" in suspension and allow it to flush easier.

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    In the Trades Gary Swart's Avatar
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    This is a link to the Laing site which has both installation methods illustrated. Going through the top is the best way as others have indicated. The auto vent can be purchased at a good plumbing supply house. Everything else is available at the box stores. http://www.hvacquick.com/catalog_fil...ion_Manual.pdf

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