PTFE tape vs Boss White

[diyjunky]

There are many threads about whether to use PTFE, jointing compound or nothing
What I wanted to know is *how* PTFE tape or jointing compound actually helps stop the leak and do they effectively work in the same way.
My theory was that the olive is failing slightly and that the PTFE or the paste is clogging up the threads and stopping the weep.
Is this correct or is it doing something else ?

Thanks.

 

[oldbuffer]

1. PTFE tape should not be applied to the threads of normal compression fittings. These threads are generally not tapered, but parallel. The joint is made watertight by the action of the compression nut squashing the olive onto the pipe, between the conical ends of the fitting and compression nut.
2. Where a compression fitting is wholly or partly re-used (for example, when a radiator valve is changed) the olive will have already been compressed on one side to accommodate the replaced fitting. PTFE tape can be wound around the olive, and will compress to accommodate the new fitting.
2. PTFE tape can be used to make tapered male threads watertight with (normally) parallel tapered female threads, for example where the threaded end of a low carbon steel pipe has a steel fitting with a female thread screwed onto it. Female threads are generally parallel because it is more difficult to cut a tapered female thread than a tapered male on.
3. Jointing compound can be used on the olive of a re-used compression fitting, or on tapered thread fittings. Like PTFE tape in fills up slight imperfections in fit which might otherwise cause leaks.
4. Not all jointing compounds are suitable for use on potable water fittings.

 

[diyjunky]

I have a compression isolator that is leaking. It’s emerging from floorboards for the hot tap of the bath. It’s really awkward to get at but do-able. I will not be able to remove the old olive. I will probably put a new straight compression coupler in place of the isolator.
In this situation, is Boss White preferable to PTFE ?

 

[diyjunky]

Got rid of the isolator and fitted a straight compression coupler with Fernox Joint compound spread on the old olives, seems fine so far ....

 

[diyjunky]

The joining compound clearly works with compression joints but what I don't understand is why these products (Ferox Hawk, Boss White etc) don't mention their suitability for this purpose. They only mention for *threaded* joints on the tin ????

 

[Madrab]

The joining compound clearly works with compression joints but what I don't understand is why these products (Ferox Hawk, Boss White etc) don't mention their suitability for this purpose. They only mention for *threaded* joints on the tin ????

Because that's not what they were designed for. They were designed for threaded joints in LCS and other threaded application materials where a gas/water tight seal may be needed. They were not designed to seal olives to their mating surfaces.

That's one use that PTFE tape is designed for.