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Plumbing FAQ: Why is my lever flush toilet not flushing properly?

This can be one of the most irritating plumbing problems that many come across and there’s usually a fairly straightforward solution. The most common type of flush apparatus inside of a lever flush cistern is called a syphon. Inside of this syphon is usually a central “plunger” which has a transparent plastic gasket at the bottom of it, this is referred to as the diaphragm washer. The most common shape of this washer is an oblong shape, however there are many different toilet cisterns and syphons that use round, square, “D” shaped and many other different shapes of washer. The shape of the washer can typically be determined by the shape of the housing at the base of the syphon which will be the same shape as the diaphragm washer.

It is this diaphragm washer that is usually the cause of problems when flushing the toilet. Over time the diaphragm washer starts to develop small tears in it’s surface, as the toilet continues to be flushed these small tears then turn into large holes in the diaphragm washer, causing the syphon to not draw up a sufficient amount of water from the cistern, resulting in a weak flush and sometimes a completely absent flush if the diaphragm washer is very damaged. Replacement diaphragm washers are usually available to be purchased separately, however in some cases there’s a deeper problem with the syphon or a replacement diaphragm washer cannot be sourced. In such a case a replacement syphon may be required.

The diaphragm washer is usually an easy part to replace, but sometimes it can be a bit more difficult. There are usually few different types of syphon a one part toilet syphon or a two or three part toilet syphon. Replacing a diaphragm washer on a one part toilet syphon can be a bit more difficult than on the other two types. This is because with a one part syphon you’ll more than likely have to physically remove the cistern from the toilet pan, which also involves isolating the water supply to your cistern. With a two or three part syphon, the part which houses the diaphragm washer can be removed from the central “stem” of the syphon, allowing you with much greater ease to replace the washer without removing the cistern.

The other type of lever flush apparatus commonly found in toilet cisterns is the lever flush flapper valve, it is extremely unlikely to experience problems with these valves as they are effectively a plug and chain mounted on a hinge at the bottom of the cistern with a rubber seal around it and an overflow tube, the only problem that usually occurs with these valves is the valve not sealing itself properly after the toilet has flushed. This would not cause a problem when flushing the toilet however, but rather water would continue trickling into the pan once the toilet has flushed – check out our advice regarding this problem by clicking here.

There are many different types of syphon from a number of different manufacturers and it can be difficult to identify which part you need for which syphon. For more advice and to check out the extensive range of bathroom, plumbing and heating consumables that we stock, visit out shop today at 314-320 Smithdown Road.