Installing 1/2" NTP Grundfos recircultion pump on 3/4" NPT Water Heater

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by CountryBumkin, Apr 20, 2011.

  1. CountryBumkin

    CountryBumkin New Member

    Messages:
    86
    Location:
    Orlando, FL
    I bought a Grundfos recircultion pump (model UP10-16BN5/ATLC) to reduce the time it takes to get hot water to the shower on the far side of the house. The plan was to install the pump in-line on the water heater outlet and the "confort valve kit under the sink in the bathroom.

    What I just noticed is that the pump I bought has 1/2"NTP fittings and my water heater has 3/4 NTP inlet/outlets. The piping into and out of the water heater is about 24 inches of 3/4 copper transitioning to 3/4 " PB where it goes into the wall. I don't know where the 3/4 pipe ends in the wall and the 1/2 PB starts, but I have not seen 3/4 piping anywhere in the house. Regardless, I'm concerned about restricting the volumn of hot water if I install the pump in-line as designed.

    My question is: 1) should I install the pump in-line in the 3/4" water heater outlet (which will/may reduce the flow) and not worry about it; or 2) should I try to return the pump (unlikely to get full refund) and buy a pump with 3/4" fittings; or 3) is there something else I can do?

    Thanks
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,889
    Location:
    New England
    Do you have a dedicated return line? If so, you could put the pump there as the size wouldn't be an issue.
  3. CountryBumkin

    CountryBumkin New Member

    Messages:
    86
    Location:
    Orlando, FL
    Thanks for your reply.
    I could run a dedicated return line. If I'm understanding the term properly. When I rebuilt my master shower/bathroom I converted the hot and cold PB lines coming out of the slab to PEX ran them up into the attic and looped them back down to the shower valve. I figured if the PB ever failed in the slab I would be able to cut the line in the attic and convert to PEX from there. So I could cut the hot water line in the attic (cap the PB side) and run a new line back to the water heater (probably 60 feet) - where I guess it would then tie into the recicultation pump (Tee'd into the water heater 3/4 line). Is this what you meant?
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
    Land of Cheese
    IMO, the 1/2" recirc is commonly installed with a dedicated return line pumping water from the bottom of the water heater at the drain port.
    Last edited: Apr 20, 2011
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,889
    Location:
    New England
    Just like the name implies, recirculation requires a loop. You either make the cross-over to the cold line, and use that to pump the water back around or create a dedicated line back to the WH (and inserting it into the bottom of the WH is the common solution). When you use the cold line to create the loop, it becomes warm. WIth a dedicated return line, the cold stays cold. So, if you put a T on the hot line, and ran a new line back to the WH (1/2" would be fine), and removed the drain valve on the bottom of the WH so you could add in a T to receive the return line, and then reinstall a drain valve, you'd be nearly there. You'd need a checkvalve somewhere in that loop.

    And, depending on the layout, you might find that the water would circulate by convection, without the use of a pump at all with a dedicated return (you'll still need a check valve).
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,486
    Location:
    Cave Creek, Arizona
    You must be trying to make a "Do it yourself" circulation system, because the Grundfos "Comfort" pump IS 3/4" and it has a female "swivel union" inlet to fasten directly to the hot water outlet and a 3/4" male outlet to reconnect the outlet pipe to it. With ANY piping below the water heater's outlet, a gravity system would not operate.
Similar Threads: Installing Grundfos
Forum Title Date
Plumbing Forum, Professional & DIY Advice, Tips & installing water hammer arrestors May 26, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Installing New Kitchen Sink - Deeper Bowls Mar 27, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Help Installing New Dishwasher Dec 28, 2013
Plumbing Forum, Professional & DIY Advice, Tips & Installing toilet drain through floor joists Dec 27, 2013
Plumbing Forum, Professional & DIY Advice, Tips & Trouble installing sink Nov 5, 2013

Share This Page