Noisy water pipe

[Jon]

After installing my bath at the weekend, I now get a fairly loud noise when using the cold tap. The tap is a mixer, the hot is from a cylinder and the cold from the main. The cold is 15mm up to just before the tap where it expands to 22mm to connect up.

I don't get the noise when the cold is on full whack, only when it is on slightly - as I turn the tap on more, the noise decreases until it stops at about 50% of the way on.

I know that due to the way the hot and cold water come through the bathroom wall, they are pretty much touching at one point - could this be the problem? Or is it more likely something to do with air in the pipework? Don't know if this makes any difference, but at the moment, the branches for the basin and toilet cistern are not connected to anything.

All help much appreciated. Jon

[Paul]

I had this problem with a pipe that went no-where. I think when you get the air out it will go away. Air is compressable - water isn't !

Paul.

[Pet]

We had it too, seemed to come from the fact the previous occupiers had a combi boiler fitted and the plumber had just looped back the cold water feed from the redundant header tank in the loft. a superb place for air to be trapped without any logical way of bleeding it off.

Chopped the whole lot out and hey presto !