I recently installed a Grundfos recirculation pump to my water system. It works great with the exception of one bathroom where the tub/shower does not have flow. I have great flow and pressure at the sink and toilet in the same bathroom just not the tub/shower. I replaced the shower valve cartridge (pfister) but it seems like maybe the anti scald is closing not allowing the water through. If I remove the cartridge I have good flow and pressure coming out. I have the same pfister set up at the farthest bathroom and it works fine. This is an older system (20yrs old) maybe install a newer tub/shower valve system? I have switched out the cartridge with the one from the other bathroom and it does not work in this bathroom but they work in the farthest bathroom. The bathroom that is problematic is closet to the water heater. Everything worked fine prior to installation of Recircuation pump so i'm thinking the anti scald is too sensitive to the warmer water circulation in the cold side water lines? Any thoughts?

 

What is the problem showers location in relation to the circulation pump? The hot water pressure at that location may be enough higher than the cold water pressure to causing problem for the balancing valve.

 

T
he recirculation pump is installed on the hot water heater. The problem tub/shower is closest in line to the recirculation pump. If there is a pressure imbalance that is causing an issue with the balancing valve what could I do to temper the pressure?

 

Are you on municipal water or a well? Do you know how stable the water pressure is coming into your home?

You could put a pressure reducing valve or valve in the line leading to the problem shower. The pressure reducing valve might work better if your water pressure varies. If the water pressure feeding your home is relatively stable a simple valve could be adjusted to cut the flow/pressure to make it closer to the cold water side.

 

Hi, You got a tough problem hope you found it. If not a couple things to try. You said the trouble started when installed a pump so shut off the pump and close the valves on the circulation pump and see what happens. Check the pump, it should pump water into the water heater.
Good Luck Woodbutcher

 

Is the recirculation pump located on the outlet pipe of the water heater, "pushing" the hot water to the faucets or is the pump located so that it "drags" the water from the heater, through all the hot water piping and then discharges back into the cold water inlet, or better, the drain tapping?

A pump located on the heater outlet may cause a problem with a balancing valve piston caused by the hot water pressure being significantly higher than the cold water pressure at the valve location.