When I turn on a faucet or shower, I hear a fairly loud rushing or whooshing sound of water in my pipes in the basement. When I shut off the faucet, it sounds like the water continues to run for about 5 seconds. It sounds like the water is repressurizing in the line. When I turn off the supply valve to my sprinkler, the sound seems to go away. Is there air in my pipes? How do I get rid of it? Is my vacuum breaker on the sprinkler line bad? Pease help.

The first thing I'd be checking is the vacume breaker, You're doing a great job of localizing the problem by shutting od branches until you see a change. Good luck and let me know how you make out. Tom