How to Replace a Toilet Flush Valve (UK, Step by Step)
Swap any UK dual-flush valve — Geberit, Roca, Ideal Standard, Armitage Shanks, Wirquin. Sizing, seals and no-leak refit.
Diagnose before you buy
A running toilet is nearly always the flush valve seal, not the fill valve. Drop a few drops of food colouring into the cistern — if it appears in the pan within 15 minutes without flushing, the valve seal is passing.
Match by opening and height
UK cistern openings are 2" (50 mm) or 3" (80 mm). Measure the internal hole in the cistern base before ordering. Height matters too — a Geberit 240.638 is 195 mm tall, a Roca AV0001300R is 240 mm.
- Roca concealed cisterns: AV0001300R or AV0002300R with dual push rod.
- Geberit UP320/UP720: 240.638.00.1 flush valve, universal to all Sigma plates.
- Ideal Standard SV93467: fits Space, Studio, Concept close-coupled ranges.
- Wirquin Jollyflush: 2" opening, telescopic 165–255 mm.
Fit without a leak
Always fit a new doughnut seal between valve and pan — never reuse the old one. Hand-tighten the plastic backnut only. A leaking flush valve nine times out of ten is over-tightening: the plastic thread deforms and lifts the seal.
Frequently asked questions
- Do I need to drain the cistern first?
- Yes. Isolate at the service valve, flush to empty, mop the last 5 mm with a sponge before pulling the valve.
- Can I fit a universal flush valve to a Geberit concealed cistern?
- No. Geberit UP frames only accept Geberit 240.xxx-series service valves — the frame chassis, actuator rod and cable location are proprietary.
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