Siphon Diaphragm (Flap Valve)
Also known as: flap valve, cistern diaphragm, toilet diaphragm
The rubber membrane inside an older UK siphon-type cistern that creates the flush action. When you press the handle, the diaphragm lifts and forces water over the siphon into the pan.
Inside the siphon unit in a close-coupled or high-level cistern. Remove the cistern lid and look for the plastic siphon tube.
Flat circular rubber disc with a hole in the centre and a small flap. Most common size is 3 inch (75 mm).
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Always turn off the water supply before replacing any part. If in doubt, consult a qualified plumber. Gas components must only be worked on by a Gas Safe registered engineer. Unvented (pressurised) hot water systems must be worked on by a G3-qualified engineer. Prices shown are indicative — check retailers for current pricing.