A couple of years or so ago our water mains were replaced and the
company used blue MDPE connected to a brass stopcock. This has been
leaking for a while - getting to a steady drip-drip-drip the other day.

Have tightened it up as much as I feel comfortable, about 190 degrees
extra turn of the nut. Rather sadly, it is still weeping.

With other pipework, I'd happily undo it, trim a bit off if needed,
replace the olive and do it up again. Having never touched MDPE before,
I am in the area of assumptions. Like, I assume there is an olive in
there (how could it grip otherwise - I don't know)! I assume the olive
is a special size. Can I buy the appropriate olive without replacing the
stopcock? Can't see one (other than standard 10/15/22/28 mm ones) on
Screwfix or Toolstation.

--
Rod