DIY Doctor UK DIY Forums

Why would you put PTFE tape on the threads of a compression fitting ?

Sorry if it seems like a rant - but it really gets to me, as I see this done on many occasions and have seen a few posts in here suggesting this is what should be done.

The threads are only there to pull the body of the fitting and the nut together, compressing the olive/ring to the pipe. The water tight seal is made between the olive/ring and the body of the fitting.

So - you need to put the PTFE tape on the olive/ring. It's only male iron connections where you would put PTFE tape on the threads.

Any other plumbers/ gas fitters / heating engineers, come across this very perculiar way of trying to make a watertight seal ?

We always put ptfe on the olive,never seen it or tried it on the threads,can't see the point

Yes [u]PTFE[/u] also known as ([b]Thread Tape[/b]) is wrapped around pipe threads (usually compression fitting parts), to stop leaks and seepage. Wrap in direction the nut turns this is a guaranteed way of stopping leaks. On the olive alone, it may develop a slow leak later, usually on cold water lines as they have considerable pressure, which is constantly changing as the taps are turned on and off in your area.

On compression fittings used on copper pipe ?

Putting PTFE tape on the threads is absolutely pointless. It doesn't guarantee no leaks - at all, it's a waste of time, it's the olive that makes the watertight seal. Not the threads.

i agree with htg it should be applied to the olive and pipe and the information i have is that it should on be only 50% of the olive
if you place any material between the threads then you run the risk of widening the gap between the threads and this will allow leaks

As a hydraulics engineer, I have seen pipe work for 40,000 Lbs. P.S.I. Working Pressure made up by the manufacturers of nut and olive type fittings and under NO circumstances should any type of thread tape, jointing compound or any other such material be used on any nut and olive fitting on the cutting ring side. Acceptable on the male thread (if one) to be screwed into a fixed female port. Further to htg's last point, I have seen many leaks caused by this.