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How To Fix A Constantly Flushing Toilet


Any flushing problem with the toilet can be a bit of a nightmare, especially if you’ve got to wait a day or more for a plumber to come and fix it.  But having a little basic knowledge about how your toilet works can be invaluable and could help you to repair your toilet yourself without the need to call on the professionals.

Most modern toilets have a direct-action cistern that operates when the toilet is flushed.  The amount of water coming into the cistern is controlled by a valve.  This valve is operated by a plastic float, which causes it to open and close according to how much water is in the cistern.  Once at the desired level, the valve should shut off and no more water should enter the cistern as the flush cycle is complete. 

If your toilet sounds like it’s continually flushing, the likely cause is a problem with the float valve or float arm, which means the float valve doesn’t shut off once the cistern is full and so water continues to flow in.  If you take the lid off and look inside your cistern, you should see an adjustable screw that allows you to reduce the level of water in your cistern.  If you try to reduce the water level but this doesn’t fix the problem, it’s likely you’ll need to replace the washer or the diaphragm, depending on what sort of valve you have.

If the water is your toilet comes from a storage tank in the loft, you’ll need to empty the tank before fixing the problem.  Turn off the mains supply and flush the toilet a few times until no more water comes into the cistern.  Take the valve out by disconnecting it from the supply pipe.  To release the float arm, remove the split pin from the valve.  You’ll then need to take off the cap at the end of the valve and take out the piston in order to unscrew the piston end cap.  You can now take out the old washer and give the cap a good clean before fitting the new washer and reassembling everything.

If you’ve got a fairly modern toilet, the chances are your flushing system uses a diaphragm valve in place of a washer valve – diaphragm valves are popular these days as they tend to last longer than washers.  However, if you do need to change the diaphragm, you’ll need to switch off the water and drain your tank in the same way.  Then you need to remove the plastic piston from the ball-valve to access the diaphragm in order to replace it.