On 07/04/2016 19:03, Lobster wrote:
I'm scratching my head a bit here. Our downstairs khazi has a slimline,
low-level cistern with a push-button flush which some family members
find very hard to operate, as it requires quite a substantial downward
force. Nothing actually wrong with it though; and I currently have the
cistern in bits with the intention of replacing the siphon with a flap
valve (http://www.toolstation.com/shop/Plumbing/p49303).

This fits in place OK, however my problem is attaching the flush pipe to
the bottom of the cistern, to connect it to the pan. Formerly, the
cistern had a single threaded collar with an inbuilt rubber seal,
intended to bear against the bottom of the siphon as it protruded out
the base of the cistern. Tightening this collar both sealed the siphon
to the base of the cistern, and the flush pipe to the siphon.

Similar to the way a compression waste fitting works?

Problem is that with the new flap-valve, the original collar is slightly
too large (different thread); whereas the new threaded collar which
comes with the flap valve does not include a rubber seal, and presumably
is not intended to seal it to the flush pipe. I get the impression this
flap valve might be intended for use only with close-coupled cisterns?

I think you might be right. I've never come across one in a low level
cistern.


The existing flush pipe does fit snugly into the base of the flap valve,
and it would probably be possible to effect a seal using lots of
silicone but I really don't want to have to go down that road!

You don't!

I'm a bit hampered by the fact that the other toilets here are
close-coupled, so I don't have any other flush pipes to examine, but
does my original system sound 'normal'? The single threaded collar
sounds odd to me. I would just swap out the whole cistern but for the
fact that it's an old coloured one (turquoise!!), which vile though it
is, matches the pan, basin and tiles...

Anyone know what I'm doing wrong, please?

I think Rogers idea of taking it to a proper plumbers merchant is the
way to go.


--
Dave - The Medway Handyman