Often considered the most overworked part of the plumbing system, all of us have at least one cistern in our homes as a part of the wc suite (toilet) in the bathroom. Apart from toilet cisterns, modern cold water storage tanks, often located in the loft space, are technically a cistern too.
The mechanisms in a cistern are probably working at least once a day, therefore over time some servicing is invariably required to keep it functioning correctly.
Nearly all types of wc cistern are relatively easy to service, the only exceptions are concealed cisterns, where access may prove tricky, and high level cisterns as a step ladder is needed.
To all intents and purposes, cold water storage tanks, located in the loft space, are a cistern too. Short of a leak (or a puncture) the only occasional form of maintenance is to ensure the float valve is working correctly - if not then the tank will overfill and leak, or not fill at all meaning no cold water from the bathroom taps.
Before commencing work on the cistern or storage tank, make sure you have all the tools you need to successfully complete the job. Use the following link for a list of basic plumbing tools:
A faulty float/ball valve is more often than not the cause of the majority of problems associated with cisterns and storage tanks. Older valves use a washer to stop the flow of water, whereas modern versions use a diaphram instead which is less susceptable to scale deposits.
The float valve allows water to enter the cistern, as the water level rises so does the hollow float/ball, at a predefined point the float reaches it's highest level and closes the valve which shuts of the water supply.
If your float valve is old, the best advice is to replace it with a modern diaphram valve. These are quite inexpensive and readily available from a plumbers merchants.
Installing a new diaphram valve
Replacing a diaphram valve
The water level in a wc cistern/water tank is controlled by adjusting the float/ball on the float valve assembly. The lower the float when the valve is closed the less water is allowed in the cistern.
This can be adjusted in a number of ways depending on the type of float valve present.
If a wc cistern will not flush, or requires the lever to be depressed a few times, then the chances are that the flush valve needs replacing.
The flap valve sits at the base of the cistern, and is operated by depressing the handle on the front of the toilet. When depressed, the lever lifts a flexible plastic diaphram (the flap valve) which allows the water in the cistern to flow through the siphon trap into the pan. As the water level lowers in the cistern, so does the flap valve until it closes over the plate, blocking the siphon and thus stopping the flow of water. As the water level rises again in the cistern the flap valve stays in place.
Replacing the flap valve
A cistern which makes a lot of noise when filling can be particularly annoying when located in a bathroom next to a bedroom. The noise is often simply caused by the flow of water, however in some instances, if the water pressure entering the cistern is particularly high, the float/ball can bounce on the surging water and send banging noises along the plumbing system.
The noise can be cured in two ways:
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