In my area we have ridiculously high water pressure. Last measured at 10.8 bar last week.
Internally - some years ago - I installed an IMI pressure reducer valve like BES 9434
The problem is that on occasions it does not completely shut off and the water pressure can creep up....stopping at a pressure that is too high and occasionally not stopping until it equalises with the supply. This can be alarming! (BTW this is my second valve of the type. They do have an integral grot-trap).
I am contemplating putting in an alternative valve and have found a Honeywell unit like this:
ps I AM in dialogue with the Water supplier about this. It would be great for them to reduce the pressure at source but but progress is "glacial".