I just noticed a very thin trickle of water running down the back (inside)
of the loo pan. Flushing the cistern didn't stop it: as the cistern
refilled it started again. The flush itself operated exactly as normal.
The flush valve is this type:
Could it be as simple as a break in the seal where the valve sits on the
floor of the cistern? Or is the fault likely to be with the valve itself?
I suppose it wouild be easy enough to replace the whole thing if necessary
but I can't find that particular model on sale in the UK.
The one you picture looks like a syphonic design, so if its letting by
once the cistern refills, it suggests that the water level in the
cistern (set by adjustment of the float valve) is marginally too high
and its overflowing down the pan.
Thanks for all the replies. The lever is at the side of the cistern. If
I'm right about where the overflow is, the the water level when full is
nowhere near that high: it's just below the 6ltr mark, which I assume is the
The leak doesn't start immediately the cistern begins to refill: it only
happens when the fill has ended. Perhaps I'm wrong about the overflow.
Here's a picture:
That isn't the overflow Bert. It would be part of the thing with the
The fill valve isn't adjusted properly, or it's FUBAR.
Turn the rod at the other end of the arm clockwise to lower the float &
that should sort it.
Dave - The Medway Handyman www.medwayhandyman.co.uk
On Wed, 05 Jun 2013 17:22:20 +0100, The Medway Handyman wrote:
If it carries on filling, the fill valve may not be shutting off
properly. May not be knackered, that type are notorious for leaking when
there's dirt or grit in them.
You clean it by:
1) Shut off the water inlet
2) Unclip the (rather fragile) white rod and float, noting the point that
it's clipped onto the rod.
3) Unscrew the blue ring and remove filter and diaphragm.
4) Clean everything and make sure the tiny holes are clear (canned air
5) Reassemble, making sure the little needle on the main part goes
through the small plastic doughnut in the diaphragm.
5) Reattach the float, water on and test.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
My posts (including this one) are my copyright and if @diy_forums on
No, that's just the back of the filling spout on the inlet valve.
The overflow is either a function of a separate 22mm PVC pipe coming out
of the side (typically) or sometimes bottom for the cistern, or by the
water level simply reaching the height of the outlet pipe on the syphon.
Once that happens, water will naturally pour over the edge of the syphon.
That's not the overflow - it's probably an air inlet to the fill valve
to prevent any chance of syphoning the water back into the water main
if the supply pressure fails.
If there isn't a separate overflow outlet pipe, then it's designed to
spill over the main syphon into the WC (which is now the norm with new
The fault is likely one of two things; the valve not working anymore,
or the fill level set too high.
Try lowering the fill level. You do this by turning that thin shaft
with the very course spiral thread on it, so the white cylindrical
float is lower. If the water comes up over the top of the white
cylindrical float when it's filling, the fill valve is knackered.
The water should lift that float, and cut off the filling, with the
float still rmaining partially above the water surface.
If the float is too high, the water will over-top the flush syphon
before it cuts off, so it will continue filling forever.
[email address is not usable -- followup in the newsgroup]
Thanks to everyone for the new replies. Several people advised lowering the
fill level: I did that, flushed the cistern, and checked the leak. It
didn't return, even when the cistern had completely refilled to its new
I left it an hour or so and looked again: the water was higher than the
original level, and actually above the top of the float. Andrew Gabriel
Well, not while it was filling, but afterwards. So it seems that the
cut-off valve isn't cutting off. I'll see if I can disassemble it and take
a look: the water here is extremely hard and things might simply be furred
If I can't fix it and have to replace the valve, two questions:
Do I have to use the same model as the existing one?
Do I have to completely remove the cistern? I've only had a quick look but
I can't see any obvious external fixing for the valve assembly. Or is it
secured purely from inside the cistern?
Something similar, but it does not need to be identical.
Look under the cistern, there will probably be a pipe running up to the
bottom right hand side with a tap connector on it. Shut the water off
(using the service valve if there is one (or using this an an
opportunity to fit one!), disconnect the tap connector
...then undo the plastic locking nut at the base of the threaded bit
that sticks out. Lift the whole valve out (have a container ready to
catch the bit of water left in the cistern after the flush.
New one drops in on its rubber washer - I normally stick some silicone
grease on both sides of it to help it seal.
Stick the lock nut back, and then reattach the tap connector. Note that
they are very easy to cross thread - so make sure you get it on dead
Thanks very much. You don't mention unfastening the central part of the
valve - the bit which leads to the connection to the pan. Is this then not
attached in any way? If it isn't, how is the seal maintained? There looks
to be a rubber washer on this part too. It was that central connection that
I was talking about when I said I couldn't see any obvious fixing on the
underside of the cistern.
I'll take a proper look at the whole assembly in the morning. There is a
stop valve in the supply pipe so at least I don't have to fit one of those.
Different valve and different purpose...
You have the flush valve / syphon. This is the thing with the green
top in your photo. That is responsible for flushing the loo. I am
assuming that this is actually working correctly - and the only reason
you are getting water flow through this when not expected, is because
the inlet valve is not shutting off completely when the cistern is
"full". Hence the level keeps rising, and eventually the level gets to
the gets to the top of the inverted U pipe in the syphon. At that point
is falls over the edge, down the outlet and into the pad. However since
it is only a trickle and does not fill the syphon pipe it does not
trigger a full flush.
Secondly you have the inlet / float valve - the thing with the blue
locknut on your photo. This senses the water level and allows the
cistern to refill. If its working correctly it will stop it filling
before it overflows. My guess is that yours sort of stops - but not
totally. So after a delay the level rises to high and overflows. The
overflow on your loo being designed to work into the pan, rather than
out of a supplementary pipe.
 These things are basically like an inverted U shaped pipe in design,
with a little flapper valve on the inlet side that can be used to "drag"
some water up the pipe. This tips the level over the top of the U and it
then starts syphoning. It keeps going until the water level in the
cistern falls below the bottom of the inlet of the syphon, and that lets
air into it which breaks the syphonic action and it stops. These have
the advantage that even of the flap valve gets leaky - it just makes it
harder to start the flush going. The valve has no involvement in
stopping the flow of water after the flush, the emptying of the syphon
takes care of that. (there are some modern light touch valves that don't
use a syphon, and do require the flap valve to seal well to stop the
water - but yours is not one of those)
I just discovered something I hadn't noticed before. John, you said:
There's rather more than "a bit" of water left. I'd say the water level in
the cistern immediately after the flush is about a quarter of what it is
when the cistern is full.
Doesn't that suggest that there's something more fundamentally amiss with
the valve than just the inlet not sealing properly?
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