Hobie wrote: You might keep

[ucodegen]

[quote=Hobie]
You might keep an eye on the gauge when someone in the house turns on faucet. Should be same pressure. If it drops=bad regulator.
[/quote]
Not quite. It will drop proportionate to the flow because the pressure differential is used to control the size of opening on the valve on the regulator. The design that does not drop much if at all as flow increases is the ‘servo’ design, two stage design or hydraulic servo design like:
https://www.zoro.com/watts-pressure-reducing-valve-6-in-flanged-115-6-fl/i/G1435497/?gclid=CKWwmo79ktICFZJefgodG04Oog&gclsrc=aw.ds
or
https://www.zoro.com/watts-pressure-reducing-valve-8-in-flanged-m115-8-fl/i/G2183885/?gclid=COOh36v7ktICFUlNfgodsUkItQ&gclsrc=aw.ds

To determine if a bad standard household regulator is bad, check if pressure can be adjusted up and down – check with slow water flow on the controlled pressure side. This will verify that the diaphragm and internal spring are working.

Now have someone shut off the slow water flow and watch the pressure – if it creeps up to match street pressure, the seat or seal on the valve is bad – or there is dirt caught in/under the valve seat.