fixing all the dripping taps..one unit (double swan neck thing in kitchen') had to be entirely removed off the two up pipes to work in.
seal was a stepped collar inside a pipe with a flat end, suppose to be a rubber or fibre washer in between, which had entirely become a smear one side and a sort of skeleton the other.
I made a 'rope' of PTFE tape and wound a new sort of ring round the collar, tightened up and its perfect.
I'd used PTFE to seal threads, but not gap fill a butt joint, before