Toilet Fill Valve
Toilet running or slow to fill = fill valve. UK toilets use side or bottom-entry valves. Easier than it sounds.
UK-specific, side and bottom entry.
Isolation valve: pipe behind toilet, flathead 90°.
Photo the setup before removing anything.
Fluidmaster 400UK fits most UK toilets.
While the lid's off, check the flush valve seal too.
Turn off isolation valve
Flush to drain cistern. Sponge remaining water
Disconnect supply hose — container for drips
Unscrew locking nut outside cistern
Lift old valve out
Rubber washer on new valve, insert into cistern
Hand-tighten locking nut, snug with pliers
Reconnect hose. Turn water on
Adjust float to fill line (25mm below overflow)
Check for leaks. Replace lid.
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