Should drip irrigation pressure regulators reduce pressure when water is not flowing?

Question

I purchased a brand new hose end pressure gauge and the water coming out of the hose faucet reads 64 PSI.

I then put a 25 psi pressure regulator between the faucet and the gauge, and it still read 64 PSI. This setup means that no water was flowing.

In total I tested two old 25 psi regulators and one new one and they all read 64 PSI.

I don't think it's a bad pressure gauge because if I turn the water on very slowly the pressure builds slowly but if I turn it on all at once the needle shoots to 64 at once.

Do pressure regulators only reduce pressure for running water for some reason or did I somehow managed to get three duds?

Answer 1

Pressure regulators are only designed to work if there is some flow through them.

If there is no flow, even a tiny amount of leakage through the regulator will eventually equalize the pressure on each side.

One major brand name includes the statement "do not use at flow rates less than 5% of the maximum rating for the device" in their specifications - i.e. at very low flow rates, the output pressure will not be properly regulated.