Knocking while water is running

[Oli]

Hello, while my water is running and for a time after I turn it off my pipes knock quite a lot (sometimes even just in the middle of the night). I'm wondering if it's the PRV because the downstream water pressure is set to 60 and will go to that after I turn the water off but will rise back to 100 within a couple minutes. I'm under the impression it should maintain that pressure (I do have an expansion tank). Before I replace the PRV I want to be sure it isn't something obvious that I just don't know enough about.
Edit: adding a picture of a similar PRV because it doesn't look like the ones I find online most often.

Thanks,
Oli

 

[Reach4]

Does that rise occur, even if the water use was only cold water?

Probably the PRV should be rebuilt or replaced. Also check the thermal expansion tank by knocking. It should be empty of water when the water pressure is 60.

 

[Sponsor]

 

[Oli]

Does that rise occur, even if the water use was only cold water?

Probably the PRV should be rebuilt or replaced. Also check the thermal expansion tank by knocking. It should be empty of water when the water pressure is 60.

I've actually only tested the pressure on the cold water tap when testing pressure. Never in combination. I would also note it doesn't happen Everytime I run the water.

 

[Smooky]

It could be a valve that is not fully open such as an angle stop under a sink or at the toilet etc.

 

[Oli]

It could be a valve that is not fully open such as an angle stop under a sink or at the toilet etc.

Thanks, I will see if I can pinpoint if it is happening only with a certain source, but it feels like most of them.

 

[WorthFlorida]

I've actually only tested the pressure on the cold water tap when testing pressure. Never in combination. I would also note it doesn't happen Everytime I run the water.

The city water pressure probably drops during the day so you are not always at 100 PSI. It may just drop enough that the PRV starts to work where as too high and it is failing. During the winter months, when less water is used, the pressure increases especially during cold nights.