My home has a recirculating system with a Grundfos 1/25 hp pump on a timer to circulate. I recently had the hot water tank replaced and at the same time converted from propane to electric. The pump needed to be slightly re-plumbed due to the different tank installations, and a new check valve was installed. The problem is now the water is constantly circulating even when the pump is off. I came across a post on this site that described a similar situation and the reply was to use a spring check valve, but the poster never replied that it did or didn't fix the problem. Would my termosiphoning problem be solved with a different check valve?

in theory, any check valve will stop thermosiphoning.
yours is either installed backwards or defective.

a spring check is a more reliable device.
BTW, it can be installed anywhere in the loop.

Dont buy a cheap spring check it will wear quickly

Thanks. Not installed backward, but possibly bad. Any simple way to tell. Does the small hex head screw on the side do anything to adjust?

Thanks. Are you saying all spring check valves are cheap and wear quickly or don't buy an inexpensive spring check valve?

you now have a 'gravity' recirculation system

count your blessings, insulate the piping (as it should have been from day 1), throw out the pump; and enjoy the simplicity

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

the hex is a rod that the gate swings on.
there should be a large hex on the top.
that will unscrew giving you a look-see at the gate which might have debris on the seat.

Not sure this is a blessing. Pipes are insulated, but heating the water to maintain set temp 24/7 is a lot more expensive than running a 1/25 hp pump for 3 minutes before a shower.

Thanks, I'll definitely troubleshoot the existing valve before replacing.

Quote

..... Not sure this is a blessing. Pipes are insulated, but heating the water to maintain set temp 24/7 is a lot more expensive than running a 1/25 hp pump for 3 minutes before a shower. .....

not really


cost of pump + cost of periodic pump replacement

cost of check valve + cost of periodic replacement

cost of 'coming up from cold' with the heating 'from scratch' of the incoming cold 'makeup' water

cost of pipe erosion from operation of pump

etc




principle is similar to heating with a heat pump: bring it up from cold or maintain moderate temp = same total cost BUT with much less wear and tear on system



remember: gravity recirc is very very slow and heat loss from properly insulated piping is minimal



simple is way way better



else: ? why are you here asking for advice ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

before pex, i used to run a gravity recirc system with insulated 3/8 soft copper.
i would install a swing check with a 3/16 hole drilled in the gate.
the flow and subsequent heat loss was minimal.

ALL the HW piping needs to insulated.

ALL

else significant heat loss from the uninsulated 1/2 or 3/4 main.


Another reason to insulate: the pipe supports/clamps should be installed OVER the insulation eliminating any frictional sounds of/from expansion/contraction (with or without a recirc system).


If done at time of installation = minimal additional labor, minor additional material cost.

Later retrofit = $$$$$$$$$$$$$$$$




ooops: the good practice versus code minimum issue .... AGAIN




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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Thanks everyone for the expert advice. Surprisingly, I didn't see any replies supporting my concern of constantly circulating hot water. So I'll give some time. For peace of mind, in the next week I plan on installing a wh meter on the hot water circuit, and run it for a week with the recirc line open and then a week with the recirc line closed. Will let you know the percent difference.