recirculating pump

[Scott Schultz]

How long do you think it would take for a grundfos type hot water recirculating pump to pump water throughout the home....2100 sq ft ranch. Buyer wants me to test the pump. First time I had someone ask me to test the pump...I can listen to see if it is pumping but don't want to stand there for 30 min. if it takes somewhere around that long....rest of inspection done though I do have to go back to check one thing that I couldn't originally which will take 3 min. but he wants the pump tested to. what is reasonable for a HI to test these types of pumps? thanks

[cduphily]

Too many variables (imho) ... 3/4" pipe? 1" pipe? Copper?, Pex? Pex 3/4 as a much thicker wall than copper (even if it's ACR) so one house with 3/4 copper will have a better flow rate than one with 3/4" pex. What is the standing pressure at the meter? size of the pump? what's the amperage rating and is the pump operating at or near its rating?

When it's all said and done it isn't a reasonable request for an HI ... we are not specialists ... time to call in a plumber/HVAC contractor If you are comfortable taking this on then charge accordingly .. it is definitely outside the scope of an HI.

[Stephen W. Stanczyk]

Originally Posted by cduphily

so one house with 3/4 copper will have a better flow rate than one with 3/4" pex.

Not necessarily. The PEX run may have very few 90 degree angles whereas the copper will have many. I would venture to say the PEX would have a better flow rate throughout the house than the copper. Now if it was a straight run only, you would be correct. Your thoughts?

[Bruce A. King]

A recirc pump should have a timer on it, just flip the switch to "on" and let it run 3-4 minutes as you inspect the house look for "almost instant hot water".

The loop may return 10-15 feet before the fixture in some cases so the hot water will not always be instant.

Make sure an expansion tank or device is present on these systems as they use check valves.

Flow rates in modern construction are already limited by the fixtures way more than 90's, pex fittings etc. The only places that will have high flow rates are exterior faucets and quality tub faucets.

[cduphily]

Originally Posted by sstanczyk

Not necessarily. The PEX run may have very few 90 degree angles whereas the copper will have many. I would venture to say the PEX would have a better flow rate throughout the house than the copper. Now if it was a straight run only, you would be correct. Your thoughts?

Good point, I'll have to pose that to a couple of friends aka I don't remember who I was having the conversation with, but giving the OD of the PEX and the OD of the copper are equal the question is: Is the initial loss of pressure through out the PEX line dramatically greater than the copper with multiple 45's /90's. I've heard (second hand) that a few plumbers are increasing to 1" PEX to supply a new home where as if they use copper supply lines they are going with 3/4".

[Brian A. MacNeish]

Originally Posted by cduphily

Good point, I'll have to pose that to a couple of friends aka I don't remember who I was having the conversation with, but giving the OD of the PEX and the OD of the copper are equal the question is: Is the initial loss of pressure through out the PEX line dramatically greater than the copper with multiple 45's /90's. I've heard (second hand) that a few plumbers are increasing to 1" PEX to supply a new home where as if they use copper supply lines they are going with 3/4".

Must be for costs only as the PEX should have less resistance and pressure drop than the copper and its 90 degree elbows.