Whining coming from capped off pipe

[fender4645]

About 5 years ago, we had a wet bar removed and the contractor capped the pipes inside the wall. This past week, the valve on our water main (the pipe where water comes into the house) broke off. We had someone come out and fix it but we can still hear a whining/whistling coming from the wall that has the capped off pipe. I'm assuming it's air in the pipes. We've ran the water in every faucet in the house, turned on every shower, and flushed every toilet. Is there any way to make the noise go away??

 

[Terry]

Do you have a PRV in the system? Sometimes those make noise.

 

[Sponsor]

 

[fender4645]

Do you have a PRV in the system? Sometimes those make noise.

Thanks for the reply, Terry. Excuse my ignorance but where would the PRV be? In the wall where it was capped? Or the main valve where the water comes into the house?

 

[FullySprinklered]

PRV is always my first suspect. Check the house pressure downstream of the prv and see if it's "normal", that is below 80lb and stable. Other possibilities include showers and outside spigots with defective vacuum breakers. A plumbing job from five years ago doesn't look much like a smoking gun to me. Check the expansion tank also to make sure it's still good while you're at it.

 

[Terry]

The pressure reducing valve is on the incoming cold, sometimes where the shutoff is.
Tracking sound is tricky. Is there a faucet nearby left open like a garden hose?