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Thread: Recirc check valve

  1. #1
    DIY Member tlarson's Avatar
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    Default Recirc check valve

    I'm replacing a 15 year old pump in a hot water recirculation system. The current system does not have a check valve between the pump and water heater (The pump discharges into a tee at the water heater drain connection).

    I'm looking for 1/2" brass, preferably sweat. Can someone recommend a part number and manufacturer? Should I use a swing check or spring style?

    I found a Milwaukee Valve 1548T12 (sweat) or 548T12 (threaded) spring style, but not sure if this is a good selection.

    Thanks,

  2. #2
    DIY Senior Member Reach4's Avatar
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    Why would you need a check valve?

    Somebody once told me that such a system could even work without a pump due to the cooler water being heavier. This person was not an authority, but he seemed enthused.

    But what I am wondering is why you think a reverse flow would happen, and what the penalty would be if a reverse flow did happen? I would think that your pump would be a very low pressure pump. Wouldn't you be concerned about the back-pressure that you would be introducing?

    I am not a pro, and I am not speaking from experience.

  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    We always install a check valve on the recirc line near the water heater. Normally a spring check.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    A gravity recirculation system can work, but if any pipe goes back up, it can easily stop the convection cycle...a pump is more reliable and likely required, especially on a retrofit. If you designed it for recirculation from the start, you might get by with gravity, but you might not be more efficient.

    Without a pump in operation, without a checkvalve, you could draw water via both the supply and return on the WH. Depending on how much water was used, it could be quite cold at the bottom, messing up your hot output. Many times, the recirc pump isn't all that big, and you potentially could pull water from both ends of the tank, regardless.
    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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    DIY Member tlarson's Avatar
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    Thanks, Jim and Terry.

    The system was designed with a pump from the start. There is a hot water return from the second story of this house to the water heater in the basement. The existing pump runs 24/7 and my replacement pump will also.

    Every drawing and piping layout I've seen for these includes a check valve. Just wondering about a manufacturer and part number. Is the Milwaukee Valve that I listed a good choice? Or, do you have other suggestions?

    Thanks, again

  6. #6
    Forum Admin, Expert Plumber Terry's Avatar
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    Grunfoss makes a clip on heat sensor that will turn the pump off when the return reaches 108 degrees.
    That way it bumps the recirc line every so often but does not constantly run.

    I pay like $8 for a check valve. I have no idea who makes a good one. I just grab the one the sell me.

  7. #7
    Moderator & Master Plumber hj's Avatar
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    quote; But what I am wondering is why you think a reverse flow would happen, and what the penalty would be if a reverse flow did happen? I would think that your pump would be a very low pressure pump. Wouldn't you be concerned about the back-pressure that you would be introducing?

    good thing you added that you are not an expert. Without a check valve the water will "backflow" to whichever fixture is next to the recirculation connection and cause cold/warm water. The check valve does NOT introduce ANY back pressure. A spring check would require that the pump produce enough pressure to open it.
    Licensed residential and commercial plumber

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    DIY Senior Member Smooky's Avatar
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    I would go with a spring check and not a swing check. Make sure the valve is rated for hot water. The information I could find for the valve you suggested was only rated for cold water.

    http://www.homedepot.com/p/t/202275512


    • Working temperature range of 33 - 212 degrees Fahrenheit
    Last edited by Terry; 11-21-2013 at 05:40 PM.

  9. #9
    DIY Member tlarson's Avatar
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    Good catch, Smooky. I won't use the Milwaukee due to the temp rating.

    I also found a Nibco that will work.

    Thanks to all for the advice and assistance.

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