toilet cistern overflow

I have a low level toilet cistern, which has never been any bother until just the other day. For some strange reason the level within the cistern is now rising too high and makes an exit out of the overflow pipe, which unfortunately is leaking from a small joint. What is likely to be causing the water to be rising about an 2 centimetres higher than it ever did before. And if I could manage to stem the leak from this overflow pipe with some tcp tape, should I not worry about the water level?
Thanks in advance douglas
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Is it a plastic float valve ? Or is it brass ?
If it's plastic, then you have to adjust the pressure pin. You do this by turning the bolt thingy on the ball arm, near the main body of the valve. Two or three turns should be enough. If this doesn't work, then you'll have to change the washer in the valve body itself. You should also see a bolt between the valve body and the side of the cistern. Make sure this is actually touching against the side of the cistern, because, if it isn't, it actually allows the valve pipe to bend with the pressure of the ball arm being forced upward by the water.
If it's brass, you might get a few more years if you adjust the ball arm down toward the water a bit. This is done by slowly bending the metal ball arm down toward the water. If this doesn't work, then you'll have to change the washer in the valve body itself. Be careful not to put to much upward lift on the ball arm, because the joint at the valve body is the weakest part of the valve and is designed not to allow the arm past a horizontal position.
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On Fri, 10 Oct 2003 00:13:08 GMT, "BigWallop"

There is also the possibility that the ball has developed a small hole, and is now "sinking" rather than floating. Easy to tell - take the ball off the arm and shake it - if it has water inside then the ball is compromised.
It is also possible that the arm on which the ball is held is rubbing against the syphon mechanism. Make sure the ball can travel up and down without catching.
The third possibility I can think of is that the small adjustment screw which causes the valve to shut off when the float rises is insecure, and over time has unwound enough to allow more water in. Wind this screw in a little (and secure with the lock nut) so that the water level is reduced.
Fixing the leak isn't the solution here, getting the water level right is.
PoP
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depending on where you live you could have a small piece of grit/scale from hard water etc blocking the valve inside. Remove the whole thing after turning the supply to the cistern of and clean it.
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The overflow is there for just such a fault where the 'ball valve' assembly has failed in some way, but the reason for this failure should be fixed otherwise you're simply wasting water.
Torbeck valves - they are the small plastic ones - can often respond to a careful clean especially in a hard water area, or replace the diaphragm if punctured. The older type with a large ball valve will probably need a new washer. Both will require the water turned off to fix, but are pretty straightforward otherwise.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Talk about curing the symptom rather than the disease!
You need to work out why the valve hasn't turned off the water before the level gets too high. Blocking up the overflow is not the solution!
Does the ball valve work? Does it stick on something? Has the ball get a leak and taken on water? Has the washer worn through?
Christian.
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