Knocking Pipes

[Rami2022]

Hello Pros.

I have an interesting situation with the water pipes at the crawl-in space. They are knocking from time to time. The interesting part is that:

• It happens when no water is in use. Neither inside the home nor outside (sprinklers)
• It always happens at nighttime (never in the day)
• It happens around the same time (7PM,11PM, 1AM)
• I think it happens to the same pipe each time.

I measured the water pressure at the main valve several times. It is 50-55.

I tried to “get rid of the air” in the pipes (shut down the water, open all faucets at home, flashing all toilets, reopen water). Same results. (No pipe knocking during that activity)

Any ideas?

Thanks in advance
Rami

 

[TomFOhio]

Maybe you have a toilet leaking through into the bowl. They will come on at all different hours. Check
your pipes and see if any are loose.

 

[Geofd]

Possibly fluctuation in the city water main a spring loaded check valve after the meter will hold constant pressure in the house, but like tomfohio mentioned check your toilet