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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...

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    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.

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    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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    My 2 cents... I didn't read the other replies... but, logic tells me not to break any seals on the water heater and don't mess with it if not necessary. If you messed up threads or broke something then you've got the possibility of having to replace a water heater ... put that puppy in the cold side and do your gambling in the gambling houses.....

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    DIY Senior Member harleysilo's Avatar
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    I recently installed a recirc pump, the type that mounts directly on top of the water heater. I am 75% satisfied with this solution. Even with it running for 15 min. on 15 min. off I still only have warm water immediately and have to weight 30 plus seconds for HOT water, 50 ft. run total. I too will be adding a dedicated return line and have been wondering the same question.

    After reading what's been posted here, and researching some I too agree plumbing it to the cold water side is the best and most logical solution.

    Less work when It's time to replace water heater and not risking running hose bib connection on bottom of heater are the prime reasons for me.

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

    Quote Originally Posted by Gary Swart
    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

    I have looked into using the Laing method of connection, but they are the only pump manufacturer that specifies the use of the air vent near the pump (before pump if connecting to drain and after pump if connected to cold inlet). They also want the pump mounted below the top of the tank. They seem more concerned about air in the line damaging the pump then the the other pump manufacturers. Does anyone follow the advice about mounting their pump or other manufacturer's pumps below the tank top. Does anyone install the air vent (Watts FV-4M1)? To install an air scoop has to be built out of 1 1/4" pipe and a threaded fitiing put on it. My plumber said it would cost around $50 just to build the air scoop.

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    In the Trades Gary Swart's Avatar
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    Install your system according to the manufacturer's recommendations. My point in posting the link to Laing was to illustrate the two places where the connection to the tank can be made and was not to imply that you should install another brand of pump using the Laing instructions.

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    Plumbing Contractor srdenny's Avatar
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    When hooking up a return to the cold side on a wh near to and below a sink or lavy I've had customers complain that they were getting tepid to hot water out of the cold tap. The easiest way to prevent this is to put a check valve on the cold side immediately upstream of the return connection, which then requires the installation of an expansion tank. This would not occur if the return were piped to the bottom of the tank.

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    In the Trades Gary Swart's Avatar
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    Actual you do get warmish water from the cold even when going into the bottom and with an expansion tank. It's not really hot water, but luke warm. The expansion tank does its job in absorbing the pressure rise when the water is heating, but a certain amount goes into the sink faucet.

  13. #13

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    Part way off the wall but you might need to think about where you put a check valve if your using your well presser tank for expiation on the hot water heater.


    PS no i can't spell

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    Plumber/Gasfitter dubldare's Avatar
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    Quote Originally Posted by Gary Swart
    Actual you do get warmish water from the cold even when going into the bottom and with an expansion tank. It's not really hot water, but luke warm. The expansion tank does its job in absorbing the pressure rise when the water is heating, but a certain amount goes into the sink faucet.

    News Flash, get out your pens and make a note.

    Water is lazy, (as are air, people, etc) it will take the easiest path.

    A check valve upstream of the expansion tank and water heater will prevent this. Also, a check valve on the inlet side of the circ pump will negate any coolish water from backfeeding when the pump is off.

    I prefer to pump into the bottom of the tank. Biggest reason why: that two-bitter of a drain valve on the wh. After installing the nipple and tee for the recirc line, put in a ball valve with a male hose adapter. A full-port drain will make flushing and future replacement a breeze.

    Also, make sure to valve each side of the circ pump.

    Pumping the recirc into the bottom of the tank will prevent any stacking/stratification that could occur. There are a few wh's (non-circulated AOSmith Cyclones) where I have had to install a short 'spin-around' pump to prevent stacking. Basically, pumping from the hot outlet to the cold inlet to increase reserve capacity.
    --Customers of plumbers: Never be afraid to ask for proof of licensure of the plumber servicing your equipment. A licensed plumber will be proud to show you his personal license.--

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    DIY Member gplumb's Avatar
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    Quote Originally Posted by dubldare

    Pumping the recirc into the bottom of the tank will prevent any stacking/stratification that could occur. There are a few wh's (non-circulated AOSmith Cyclones) where I have had to install a short 'spin-around' pump to prevent stacking. Basically, pumping from the hot outlet to the cold inlet to increase reserve capacity.
    What do you mean by "stacking/stratification"? When the recirc return line is put into the cold water inlet at the top of the tank it feeds to the bottom by way of the dip tube. Why would this be any different than feeding the return warm water externally to the bottom of the tank by way of the drain connection point?

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