Water Pipes behind plaster - problems!!

[krspa9]

I've had a new kitchen fitted and I sunk the orig water pipes into the walls to be plastered over. About a month ago I noticed that all the plaster was damp and so knocked it off to discover a joint had started leaking.

I got someone around to solder the joint. I've left it a couple of weeks to make sure it wasn't leaking before re-plastering and the joint looked fine. I checked it every day and it was dry.

Having re-plastered, the plaster is dry but whenever I dont have the heating on a damp patch grows around the joint. When I turn the heating on the patch disappears as I presume the hot pipe is drying the patch out but when I turn it off the patch starts growing again. Before I re-plastered the pipe only leaked when I had the heating on whereas it seems to be the other way around now. I presume this means the pipe is not leaking. Would damp be condensing on the pipe when the heating is off and soaking into the plaster?

If anyone could help it would be much appreciated. Thanks.

 

[bathjobby]

Plastering directly onto copper pipes will cause them to corrode and leak. They should be in a conduit or use none copper.

 

[krspa9]

As soon as the plaster is applied shouldn't affect them though should it?

 

[croydoncorgi]

If there's a 'damp patch' around the joint with the system cold then, sorry to say, the joint is leaking! If the mark disappears with the system hot, it's a small leak!

The only way the damp could be appearing from somewhere else and only coming to light around the joint is if there's some way it could run down the pipe until it hits the joint and only then is in contact with the plaster. You haven't told us enought about the situation - especially whether the pipe is definitely in contact with the plaster all the way down the wall. Definitely worthwhile to check for leaks in exposed parts above the spot before ripping the wall open again.

(I agree that bare pipes in plaster is bad practice - but I've never found a copper pipe corroded through by contact with gypsum plaster. What WILL gives loads of grief due to damp marks is a cold rising main embedded in plaster - the coldness causes attracts moisture as condensation which then soaks back into the plaster.)