Toilet cistern not filling or filling too slowly
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Most likely cause & what to check
Turn off the water supply to the cistern using the isolation valve on the supply pipe.
Flush the toilet to empty the cistern.
Modern toilets have a bottom-entry float valve (Fluidmaster type) — the fill rate is adjustable via the adjustment screw or clip at the top of the valve.
If the valve is not filling at all, it may be seized — try turning the adjustment screw. If it won't move, replace the valve.
To replace: undo the locknut under the cistern and the water supply connection. Fit the new valve at the same height and reconnect.
Turn the water on and adjust the water level using the float arm — the correct level is 25mm below the top of the overflow tube.
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