Knocking Pipes

[Dorit2022]

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, Dorit

 

[James Henry]

Varmints

 

[Sponsor]

 

[WorthFlorida]

Is the noise from the pipe itself without moving or is the pipe loose hitting a floor joist or a bracket? The pressure gauge, does it have tattle-tail needle that gets pushed and remains at the highest pressure reading? What type of pipe is it? Copper, CPVC, PEX, or galvanized steel? Do pipes run through the holes drilled in floor joist or are all hung with clamps or brackets?

If the times are pretty consistent, maybe the water plant/pumps are being serviced and pumps are being taken on and off line?

What you may need to do is have someone in the crawl space wiggle the pipes and you inside the home maybe you can tell from the noise which pipe is doing it. Brackets and clamps can work loose overtime.

 

[Weekend Handyman]

Varmints

Yup … if it is PEX, I would look for bite marks.

 

[Jeff H Young]

so the pipes make noise when no water is used. what about when water is used open and shut fast? no noise? if not I wouldnt expect strapping. surges could be issue in main from other sources , rats, cats, possums etc possibilitys. you gotta start somewhere . pressure gage might give an indicator as suggested if the red needle bumps up 20 pounds that tells you its water use related

 

[Tuttles Revenge]

Do pipes run through the holes drilled in floor joist or are all hung with clamps or brackets?

This is what I would be looking at. The piping is cooling down and the slight contraction is pulling against a hanger or bracket that its being supported by. Very common in copper with J-Nails or PEX with Inserts/Isolators in holes.

 

[Jeff H Young]

There are a whole lot of things to look at , the night cool off could be it .

 

[Mr tee]

I'd check to make sure a toilet isn't leaking. It could be when the fill valve shuts off after filling it causes something to move.

 

[Reach4]

Interesting problem. Get that pressure gauge. Point your cellphone at the gauge before one of those times, and record a movie. If you hear your noise, note the time, and look at the movie for that time. Did the gauge jump, or not?

Also, consider de-powering your irrigation system for a while. Does the noise still happen? The irrigation controller has a timer, so it becomes a suspect.
I don't know if being de-powered for a couple hours messes up your time of day clock in the irrigation controller.