Foghorn Sound?
I am getting a foghorn sound from the main water line, where it enters our home, prior to the pressure relive valve. This occurs whenever there is a water demand of any level (example: flushing a toilet). No solutions attempted!

Do this:

1. Water Pressure Regulator has an adjustment screw on top of the cylinder. Turn it 1/2 turn in either direction

2. Turn OFF and back ON main water valve in the same location

See if that helps

Milo

Most likely the PRV needs to be replaced if adjustment doesn't solve the problem.

I wouldn't hurt to call your own water supplier to make sure they are not having issues in your area before you make any adjustments.