On Tue, 23 Feb 2016 10:30:20 +0000, Stuart Noble
wrote:

snip

If there's a washer of any sort involved, I'd replace that from my pack
of Aldi 500 assorted washers (reducing it to 499).

Hehe.

Seriously, the washer
in waste compression joints often looks ok but isn't.

I've also had it where it looks f'd but had to use it and it's worked
fine, but then I guess there are important places and less important
places.

Like, if you have a conventional waste (like on a shower) you only
need to get a good seal around the back on the flange, or the waste
fittings that fasten with a screw from above (so no thread to leak
underneath). However, as soon as you have something like an overflow
(that uses the same final outlet / fitting as an assembly) you don't
need a seal under the flange at all (although you would to stop stuff
getting under there) as it's not actually stopping any water getting
past.

Cheers, T i m