Firstly, if you're going to use PTFE to seal a compression joint in a water supply pipe, is it possible to use too much tape? And by "too much", I don't mean ten or twenty turns, but maybe three or four.
Secondly, is there any benefit to be had in adding a smear of silicon mastic to the thread before putting on the tape? I ask because as an occasional DIY plumber I sometimes have trouble sealing compression joints, and I think I may be doing something wrong. In all cases I clean the pipes, then apply two or three turns of tape to the threads along with a smear of silicon. Sometimes I put one turn of tape on the olive too.
Case in point right now is a particularly stubborn isolating valve which I've fitted in a pipe run to an outside tap, which despite silicon, tape and parts having been well cleaned before assembly is still weeping; and this after being nipped up several times with a spanner to the point where I daren't nip anymore.
Secondly, is there any benefit to be had in adding a smear of silicon mastic to the thread before putting on the tape? I ask because as an occasional DIY plumber I sometimes have trouble sealing compression joints, and I think I may be doing something wrong. In all cases I clean the pipes, then apply two or three turns of tape to the threads along with a smear of silicon. Sometimes I put one turn of tape on the olive too.
Case in point right now is a particularly stubborn isolating valve which I've fitted in a pipe run to an outside tap, which despite silicon, tape and parts having been well cleaned before assembly is still weeping; and this after being nipped up several times with a spanner to the point where I daren't nip anymore.