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.

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?
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!

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?


--
David

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.

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?
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!

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?




Blimey, I've never seen a flush valve like that. But it looks as if it's
designed for close-coupled cisterns. There's a flange and rubber washer
on the inside and a big plastic nut on the outside. There's a bit of
thread sticking out after the nut is done up, and you would normally put
the doughnut round that.

I would have expected all flush valves - of whatever type - to use
standard BSP threads, so I'm surprised that your old fitting to attach
the flush pipe doesn't fit. How much too big is it, and how different is
the thread. Could it be persuaded to tighten up if you wrapped lots of
PTFE tape round the threaded bit?

It might just e woth taking the flap valve and the flush pipe to a
plumber's merchant to see whether they have a different type of nut
which would fit.
--
Cheers,
Roger
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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

On 07 Apr 2016, David Lang grunted:

On 07/04/2016 19:03, Lobster wrote:
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?

Exactly.

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.

That said, I've just noticed that the instructions talk about
disconnecting and refitting the flush pipe, so presumably not! (see
http://tinyurl.com/gtl95fu or
http://www.heatandplumb.com/brochure...per_valve_leaf
l
et.pdf

It's odd though that although the length of the threaded outlet of the
flap valve is the same as on the old siphon job, due to the effective
depth of the base of the cistern (a whopping 35mm due to a reinforcing
circular rib around the outlet hole) once the single threaded collar is
applied there is no remaining thread exposed anyway, for a second
sealing collar to be attached.

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

Yeah, maybe so.

FWIW I've also found a supplier of spares for the original cistern (of
no direct use to me as mine isn't actually faulty, but there's a picture
of the beast he http://tinyurl.com/jatyxv3 and the siphon he
http://tinyurl.com/j2hco6d (you can see that although the i.d. of the
threaded outlet is a standard 1.5", the walls are much thicker there
than in a 1.5" compression fitting, so the thread size is not standard.
(Roger - the difference is far too much to fill with PTFE!)


--
David