Cistern Not Filling or Filling Very Slowly

The cause is usually a misaligned or jammed float valve, or a dirty filter screen on the inlet valve. Step 1: Remove the cistern lid and check that the float moves freely without catching on the cistern walls – gently straighten it if necessary. Step 2: Turn off the water supply, unscrew the inlet hose and clean the small filter screen using a toothbrush under running water. Step 3: Reconnect everything and test that it works correctly. If the valve is heavily scaled or faulty, replacing the fill valve (approx. £8–15 from a DIY store) is usually the most lasting solution.