Redeye wrote:
okay, thanks for the feedback.

i've come to the conclusion that i've followed bad advice which is
probably the cause of the problem. i'd also been warned not to
overtighten compression joints, but advice here seems to suggest that
isn't possible.

I think it is. If you tighten it up as far as it will go, if you need to
take the joint apart at any future date you'll have a hard time getting it
watertight again as there's nothing left to compress.

Tim