Our bathroom toilet cistern - fitted when the bathroom was refurbished
in the early 1990's and not touched since - had become very difficult to
flush, and it was pretty obvious that the syphon was shot. It's a
close-coupled toilet with a fairly heavy vitreous cistern, which was
fitted with a conventional lever-operated flush syphon and bottom entry
ball valve, and bottom entry overflow pipe - discharging to the outside
world.

I decided to replace the syphon with a button-operated dual-flush valve
like this
http://www.toolstation.com/shop/Plum...h+Valve/p65429
and the fill valve with one of these:
http://www.toolstation.com/shop/Plum...k+Valve/p32359

The job is now done. [I could write a book about why it took me a whole
afternoon to get it apart, but I won't bore you with that!]

I do have a few questions, though, for future reference - because I have
another toilet in the en-suite which may get the same treatment even
though its flush isn't *too* bad as yet.

The dual-flush valve has its own adjustable overflow pipe, which
discharges into the pan - potentially doing away with the need for an
external overflow. But:
(a) I already had an external overflow which would have been more
trouble than it's worth to disconnect and blank the hole in the bottom
on the cistern, and
(b) I think I'm more likely to notice water dripping from an external
overflow than dripping into the pan - and I'm on a water meter!

So, what do people normally do when doing a refurb which results in 2
overflows? I've set the adjustable one on the new flush valve a bit
*higher* than the original overflow pipe so that it will only discharge
into the pan if the original one can't cope for some reason. Does that
sound reasonable?

The new fill valve is adjustable for height. It has a "critical level"
indicator and the blurb says that this must be at least 1" above the
overflow level. But if I do that, the top of the fill valve is too high
to fit the lid! What am I supposed to do? I could potentially cut a bit
off the overflow pipe - or adjust the new valve's overflow to a lower
level so as to discharge into the pan rather than outside. But the
overflow level would then be dangerously near to the normal fill level -
so it could only over-fill by a tiny amount before overflowing.

So, what's this "critical level" business all about, and what are the
likely consequences of disregarding it?

I imagine that a few of you fit quite a lot of toilets, and must have
come across these issues.
--
Cheers,
Roger
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