I've just plumbed in a complete bathroom and extended the CH system upstairs. The CH i did using copper end feed joints and it went without a hitch. I've used a mixture of plastic and copper for the bathroom using standard compression fittings as i'm wary of using push-fit, especially as the floor will eventually be tiled. I used no jointing compound on the plastic pipe, and many of the joints are weeping now i've connected up the mains. I believe all of the suspect joints are the plastic ones. (I used purimachos compound on the copper joints, tho' i now realise that it's not suitable for potable - my mistake!) I was advised not to use compound by a plumber, who also said i should never use a linseed based one on plastic as it will degrade it. However, looking at the many types of compound available, none i have seen is recommended for copper pipework only. So i intend to do all the joints again with compound and hope that cures the problem. The question is, what's the best one that is OK for copper and plastic and hot and cold potable water? Any constructive comments most welcome. Thanks.