Mysterious thumping in plumbing?

We have been bothered by a thumping sound that appears to be associated with our cold water. The sound is regular/rhythmic - like one of the turbines on the roof is hitting something with each turn - but that's not it. Can hear it best close to where the water line enters the house (from inside house). But, is audible (and you can feel it in the pipes) underneath most every sink. We cannot MAKE it happen - sometimes using the clothes washer will trigger it. I can make it quit most times by turning on the sprinkler system for a couple of minutes (I hear a bigger cu-chung when I do, but then the thumping stops). Also is heard (slightly) and felt at the main water valve in the front yard (thumping stops when I shut off water. If I leave it off for a few min and turn water back on - no thumping).

Is this a PRV that's gone bad? Would this be inside a wall? How do I know I have one? Gotta get this solved!

Thx.

 

Welcome to the forums.

It you had a pressure reducing valve it can usually be found near the water meter or where the main water service enters the house if your meter is outside.

Your problem sounds like water hammering. There are several ways to stop it but one of the easiest is to turn the water main off. Open faucets up around the house. Allow water to drain. Close all the valves and turn the water back on. The faucets will sputter for a while but what will happen is an air cushion is usually trapped in the plumbing to stop the hammering.

A quick 5-10 minute fix.

A simple screw on gauge would allow you to check for a high water pressure issue.
Pressure Gauge-91130 - The Home Depot

 

I will give this a try .... If I knew how to make it happen, then it would be easy to tell if it worked. Will keep you posted. Thx!

 

Usually it occurs whenever you run a lot of water and shut it off instantly.

A toilet valve, a dishwasher fill valve, a clothes washer fill valve.

You said it happens often so if the noise is gone.... you did good.