Hello.
Cold water pressure relief valve start to drip water through the drain pipe. I replaced it with a new one but it is also dripping water. I have reduced water pressure in the house to the minimum by turning main water supply valve but it still leaking.
Thanks for your help.

Closing main water supply valve half way doesn't reduce pressure.

There are 3 main reasons Pressure Relieve Valve leaks:

1. Faulty PRV ( replace PRV )
2. Pressure to high ( reduce pressure at the regulator or replace it with new one AND replace PRV )
3. Thermal Expansion ( Install Thermal Expansion Tank + replace PRV )

Thank you very much for your quick respond.
I've replaced PRV two times and both dripping water.
I've reduced pressure at the regulator (not by closing half way main water supply valve). I guess I'll try Expansion Tank.
Thanks again.

Invest in a hose bib water pressure gage so you KNOW what's going on instead of guessing: Water Pressure Gauge w/ Garden Hose Adapter - FreshWaterSystems.com (http://www.freshwatersystems.com/p-994-water-pressure-gauge-0-150psi-glycerin-filled-w-garden-hose-adapter.aspx)

You will then be able to isolate PRV and expansion tank issues.

1. PRV bad when pressure is unregulated when any valve is open in the house even a small amount.

2. Expansion tank test:
1. turn off water heater until cool (overnight)
2. Don't use any water. Monitor pressure.
3.Turn on water heater.
If pressure increases significantly as the water heats up the expansion tank is faulty.


It's unclear if you have an expansion tank. Set pressure to about 50 PSI.

Is there a sprinkler system or a backflow preventer, (see image) installed? What's the house water pressure after you reduced it? Let me know. Tom

Is there a sprinkler system or a backflow preventer, (see image) installed? What's the house water pressure after you reduced it? Let me know. Tom
Hi, Tom
Thank you for your respond. I've purchased today water pressure gage and it show 61 psi. (I actually increase it back since with the lower settings PRV was dripping water any way.) PRV stamped 75 psi. We do not have sprinkler system and back flow preventer in the house.
Mike