Jim GM4DHJ ... wrote:

On 27/08/2019 10:26, Roger Hayter wrote:
Harry wrote:

Lee Nowell expressed precisely :
I am installing a new shower tray and the waste it comes with has a very
thin washer that goes on top of the tray and underneath the waste
fitting. Is this enough to seal the top or should I silicone it on to
the tray? Or I guess fit it and silicone around it?

Put some Plumbers Mait around the sealing points, plus long the threads
too, to be sure of no leaks. It's none setting, so comes off easily
where it squeezes out or if it needs to be disassembled later.

If I remember rightly I don't think the washer on top *is* an important
sealing point, as the metal part is open underneath. It just stops
water bypassing the plug, and a slight ooze does not matter. The seal
is to the underneath of the tray, and this is where sealant is best
used.

correct

Except that we're probably thinking about sinks with integral overflows,
and maybe shower trays and baths don't have plugs or integral overflows,
so the seal on top may be more valuable, It still looks messy having
sealant on top, but if you don't then you need to seal the threads of
the back nut as well as the face.

So I withdraw my comment.

--

Roger Hayter