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

Users who are viewing this thread

CountryBumkin

Active Member
Messages
915
Reaction score
70
Points
28
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
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
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.
 

CountryBumkin

Active Member
Messages
915
Reaction score
70
Points
28
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?
 

Cacher_Chick

Test, Don't Guess!
Messages
5,458
Reaction score
213
Points
63
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:

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
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).
 

hj

Master Plumber
Messages
33,602
Reaction score
1,038
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
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.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks