We have a circulating pump for our hot water tank - the pump sits between the tank and the line going into the house. The issue i'm facing is if the pump is not running, I get endless cold water to the bathrooms that are closest to the return side of the line/loop.

I am thinking the check valve is stuck in the open position, you can see in the picture below that there is some calcium buildup that came out of it at some point in the past. When I suggested this to the guy at Lowes (he said he was a former plumber), he said it's not possible for water to go from a 3/4" line to a 1/2" line due to some kind of "pressure" reason (I couldn't remember his exact reason). He said the water should continue to flow in the loop in the same direction as always, even if the check valve is broke. I asked what is the purpose of a check valve then, and he said high pressure buildup. He said I might have a slab leak somewhere (this made zero sense).

Hoping someone can confirm that if the check valve is indeed stuck in open position, and the pump is turned off, then it's possible that could explain why the hot water in the sinks and showers closest to the check-valve side of the line, is getting cold water. If it is indeed the check valve, do I need to replace the whole thing, or can it be opened from the top to see if it can be freed up?

enter image description here

  • I think you may have misunderstood the pressure thing the plumber told you, but your assumption about the check valve seems reasonable. Can you disassemble it and clean it up with vinegar or CLR? It looks like a serviceable unit, so you can probably just replace the guts if you prefer.
    – isherwood
    Jan 14, 2019 at 21:53
  • The pipe size thing was probably related to this: diy.stackexchange.com/questions/85770/…
    – isherwood
    Jan 14, 2019 at 21:57
  • Thanks @isherwood, I am willing to do that, but if it doesn't work successfully ( it won't re-assemble correctly ) then I will go the replacement route, and I will want to redo the way the TPR valve line and hot water return line connect to the tank - add flex lines that I can screw on/off. That design will be another post.
    – Greg
    Jan 14, 2019 at 22:00
  • please post a closeup picture of the check valve assembly
    – jsotola
    Jan 16, 2019 at 1:35

1 Answer 1


I know this is a year later, but I finally got around to getting this addressed. I decided to service my water heater - drain the tank, replace the anode rod, and replace the check valve. Sure enough, the inside of the valve was gummed up, with the little disc stuck in the open position. This most likely explains why our tub could get "warm" water instead of "hot" water after a few minutes.

enter image description here

  • For the check valve, I replaced it with a SharkBite check valve, simply because it would be easiest and quickest fix. We got lucky with the sweating of the copper to the main line, and it was a huge mess. I suspect it will gum up as well over time, I am hoping by leaving the hot water circulator running continuously 24x7, it should mitigate it.
    – Greg
    Feb 5, 2020 at 21:39

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