mangoManFT
New Member
I recently had an under-sink Metlund D'mand hot water recirculation pump installed, using the cold water line as the return. Normally it works fine. However, I noticed that if I run my lawn sprinklers, I get hot water out of the cold tap, implying the hot water is being sucked through the pump to the cold side. The feed to the irrigation is right near the bathroom where the pump is installed.
I contacted the manufacturer and they said the drop in pressure when the sprinklers are on is overcoming the 20 psi rating of the pump's IFC valve and it is opening allowing the hot water to go through. They suggested putting a 25 psi spring-loaded check valve on the cold side to overcome this problem. I am not a plumber, but I have a technical background, and want to understand this issue and solution a bit better. I am seeking answers to the following:
1) I'm guessing the 20 psi rating on the pump's IFC valve means that if the pressure differential between the hot and cold sides goes over 20 psi the valve opens - is this correct? And what does IFC stand for? Internal Flow Control?
2) The 25 psi rated spring-loaded check valve should be installed with the flow direction being pump => cold water line, correct? Can't see how it would work otherwise, but want to be sure.
3) How does the proposed solution work? Do the two psi ratings add up because they are in series and therefore the differential needs to be 45 psi in order for both valves to open?
thanks for any advice/knowledge you can share!
I contacted the manufacturer and they said the drop in pressure when the sprinklers are on is overcoming the 20 psi rating of the pump's IFC valve and it is opening allowing the hot water to go through. They suggested putting a 25 psi spring-loaded check valve on the cold side to overcome this problem. I am not a plumber, but I have a technical background, and want to understand this issue and solution a bit better. I am seeking answers to the following:
1) I'm guessing the 20 psi rating on the pump's IFC valve means that if the pressure differential between the hot and cold sides goes over 20 psi the valve opens - is this correct? And what does IFC stand for? Internal Flow Control?
2) The 25 psi rated spring-loaded check valve should be installed with the flow direction being pump => cold water line, correct? Can't see how it would work otherwise, but want to be sure.
3) How does the proposed solution work? Do the two psi ratings add up because they are in series and therefore the differential needs to be 45 psi in order for both valves to open?
thanks for any advice/knowledge you can share!