I have a very annoying problem. We bought a townhouse in 2010, April. When we were buying the house, we heard a water whistling noise when the water was running in the bathroom. The Realtor told us that we need to adjust the valves, let the water run and will take the air out of the pipes that's creating this noise. As first time buyers we didn't think much of it. We later realized that the pipes whistle when - 1 - washer(upstairs) is running, when we turn on the cold or hot water in the two bathrooms (upstairs), when the showers are running (upstairs), when I flush the toiler downstairs, it whistles upstairs.

The noise goes away when the flush the toilet in one of the bathrooms for sometime like at least couple of hrs, until further whistling. Here is the kicker, in the middle of the night, I don't think any water is running, the whistling comes back again.

I tried a few things to solve this problem yet still no solution. I cut the water from the main line, and opened every faucet, and completely get all the water out. Shut the valves for each sink, toilet, etc... and turned the main water line on. And then turned the water back on in each location one by one. Helped for a day, and it came back again.

I squeezed the valves down to lower pressure also, I heard that may help, still no solution.

Here is one more thing which may be the reason, in the bedroom shower, the hot water runs with good pressure, but when I try to turn faucet to cold, the water pressure becomes weak. I don't know if that has something to do with it.

Any suggestions? Solutions? And if I call a plumber what type of work you think will be and how much you think it will cost? We are a normal family with financial concerns so I am looking for honest answers.

Thanks
Oz