Toilet repairs

How a toilet works

Ever wondered how the little bit of water in your toilet cistern pushes everything ahead of it down the sewer pipe when you flush? Well, it doesn’t do it all by itself. The toilet bowl and pipes are also designed to work as a siphon, sucking everything away.

How a toilet works

How to fix a running toilet

The water keeps running into the bowl after you have flushed, or water is running from the pipe on the outside wall.

These symptoms could result from the filler float in the cistern being set too high, causing an overflow problem; a worn or bent intake washer; or a worn or bent cistern washer. Read under the following three headings to determine where the problem originates.

Always do your plumbing chores on a day when the plumbers' supplies store is open.Take a sample of the spare part with you... or maybe a photo on your cellphone.

An overflow pipe problem or a worn or bent intake washer

In a perfectly working toilet, the intake valve and its washer control the flow of water coming into the cistern. Once the toilet has been flushed and the cistern is empty, water enters through the intake valve. The float rises as the water rises and when it reaches the top of its path it turns off the intake valve so that the water remains at that level until the toilet is flushed again. The water level in the cistern should be about 12 mm below the overflow pipe.

All cisterns have an overflow pipe to prevent flooding if the flush mechanism isn’t working properly. On older toilets, it leads from the top of the cistern out through the wall of the toilet cubicle. In modern toilets it leads back down into the bowl.

So the first thing to check is whether water is running or dribbling into the overflow pipe. If it is, you’ll have to adjust the float so the water level is about 12 mm below the overflow pipe.

If the float is an old-fashioned ballcock (i.e. a plastic or copper ball on a metal arm that runs across the top of the cistern), check to see if there is a lock nut and screw at the intake valve end. Find this by flushing the loo and watching to see where the water enters the cistern.

     To be able to work in a dry cistern, turn off the inlet tap and flush the  toilet.Undo the lock nut and adjust the level of the arm using the screw. (Some ball-cock mechanisms have a hinge part-way along the arm.)

     Adjust the lock nut or screw to lower the arm. If neither of these exists, you’ll have to bend the arm downwards so that the float will sit lower.

     Hold the end of the ballcock arm around the intake very firmly so that you don’t bend or put pressure on the intake valve and bend the arm downwards.

     Now, when the cistern fills, the ball-cock will shut the intake valve off sooner and the water level should be lower. If this doesn’t solve your problem there is something wrong with the valve on the end of the ball-cock arm. See www.practicaldiy.com for instructions on how to replace washers in slide valves (quite complicated) or call your plumber.

In more modern cisterns the float is generally a cuboid plastic one running up and down below the intake valve. The height of this, and therefore the water level, can easily be adjusted by screwing the fitting at the top of the arm or plastic chain that controls the float. Sometimes there‘ll be a clip on the wire on which the float runs up and down.

    Squeeze the clip and move it down on the guide wire.

    Flush the loo and check the water level when the cistern fills.

    Adjust the clip until the level is 12 mm below the overflow pipe.

    If the intake valve continues to leak after the float has risen, you’ll need to undo it and replace the washer inside.

    Turn off the water inlet tap on the outside of the cistern first or, if there is none, turn off the water at the mains before you start work. A leak could also develop in the joins between the brass fittings. If this is so, unscrew them and wrap thread tape about eight times around each thread before screwing them up again.

A worn or bent cistern washer

The cistern washer is located at the bottom of the cistern between the flush valve and the flush pipe. If it is worn, water will constantly bypass it so it’ll need to be replaced. Sometimes the fault can be as simple as a bit of debris being lodged under the edge of the washer so it doesn’t seat properly. This simply needs to be cleared. After turning off the water at the mains or inlet tap, flush the cistern. This’ll give you a dry cistern to work with. 

Delving your way through all the flush mechanism parts can be tricky but it’s worth a try, particularly in an older-style cistern where the parts are all separate. At the entrance to the flush pipe is a washer. Prise it off and take it to the plumbers’ supplier to get a replacement.

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