On 09/06/2021 08:37, fred wrote:
Anyone wrap olives in ptfe ?

I've only just figured out what you meant.

The standard advice is that you should not, presumably on the principle
that any foreign matter across the sealing face could prevent the
formation of a good seal.

While that might (or might not) be true of, say, hemp, I don't believe
it would be an issue for PTFE because of its very low "flow pressure".

That said, personally I avoid putting it over an olive but I *do* use it
on the male threaded portion, because the low friction means you get
more "pinch" for a given torque.

It does not, in general, provide sealing even with multiple layers of
tape on the threads because there is still likely to be a leak path back
along the pipe. Although for tap connectors, lengths of tape twisted
into a rope and wound round the pipe as a sort of backup to the fibre
washer will sometimes provide a seal, especially for DHW where the
pressure is lower than the cold main.