Plumbing and maintenance
Cistern internals: how the flush and fill actually work
Understanding the three parts inside a cistern, flush valve, fill valve and overflow, makes most WC faults obvious rather than mysterious.
The practical points
A dual flush valve that never fully seals is the most common cause of continuous water loss in modern cisterns.
Concealed cisterns need an access panel because these parts are consumables, not permanent fittings.
Frequently asked
Are parts universal?
Many are, but concealed frame systems often need the manufacturer's own components.
How long do they last?
Several years typically, less in hard water where scale attacks the seals.
Where this fits with our work
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