A: Bill, with plumbing you can never be certain as to what is causing an issue unless you can actually trace out the lines and see the problem with your own eyes. I recommend you call a licensed plumber to check this because it sounds like you may have a hidden leak somewhere in the house.

A "sill cock" is an outside water faucet where you connect your garden hoses. So, if the valve label is correct, the whistling noise may indicate that there is a small leak somewhere after the shut off valve to the outside faucet.

Hopefully the pipe is exposed and you can spot the leak. But, if the sill cock line runs underground or through walls, this can be a bigger issue to find and fix.

Don't wait on this one. Slow hidden leaks can cause water damage to your home, and that whistling sound you hear is not a happy tune!