How to Get a Toilet Cistern to Flush

How to Get a Toilet Cistern to Flush

How to Get a Toilet Cistern to Flush When you depress the flushing lever on your toilet cistern, it lifts a perforated plastic or metal plate at the bottom of an inverted U-bend tube (siphon) that is fixed to the base of the cistern. As the plate rises, the perforations are sealed by a flexible plastic diaphragm (flap valve), so that the plate can displace a body of water over the U-bend to promote a siphoning action. The water pressure behind the diaphragm lifts it again so that the contents of the cistern flow up through the perforations in the plate, over the U-bend and down the flush pipe. As the water level in the cistern drops, so does the float, opening the float valve to refill the cistern.

If the cistern will not flush until the lever is operated several times, the flap valve probably needs replacing. If the flushing lever feels slack, check that the wire link at the end of the flushing arm is intact.

Essential tools:

  • Adjustable wrench
  • Pliers


Three part syphon

This type of syphon can be dismantled for replacement of the flap valve without having to shut off the water or drain at the cistern.

Changing the Flap Valve

If the WC cistern will not flush first time, take off the lid and check that the water level is up to the internal mark and that the flushing lever is actually operating the mechanism. If it seems to be working normally, replace the flap valve in the siphon.

1.   Before you service a one-piece siphon, shut off the water by tying the float arm to a stout batten placed across the cistern. Flush the cistern.

2.   Use a large wrench to unscrew the nut that holds the flush pip to the underside of the cistern. Move the pipe to one side.

3.   Release the remaining nut which clamps the siphon to the base of the cistern. A little water will run out as you loosen the nut, so have a bucket handy. (The siphon may be bolted to the base of the cistern instead of being damped by a single retaining nut.) Disconnect the flushing arm and ease the siphon out of the cistern.

4.   Lift the plastic diaphragm off the metal plate and replace it with one of the same size. Reassemble the entire flushing mechanism in the reverse order and attach the flush pipe to the cistern.


Making a new wire link

Retrieve the pieces of broken link from the cistern, then bend a new link from a piece of thick wire. If you have thin wire only, twist the ends together with pliers to make a temporary repair.

07. December 2010 by admin
Categories: Plumbing | Tags: | Comments Off on How to Get a Toilet Cistern to Flush


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