Quick checks
- Is water on elsewhere in the house?
- Is the toilet isolation valve fully open (slot in line)?
- Is the float caught on the cistern wall or flush valve?
- Has anything been done recently that may have put grit in the pipes?
Clean the fill valve
- Turn off the isolation valve.
- Remove the top cap of the fill valve (most twist off).
- Take out the diaphragm or seal and rinse it.
- Hold a cup over the valve and turn the water on briefly to flush grit out.
- Reassemble and test.
Pro tip: Some valves have a small filter where the supply pipe connects. Remove and clean it.
Low-pressure and high-pressure valves
Older ball valves come in high- and low-pressure versions. A high-pressure valve on a low-pressure loft tank fills very slowly. Modern universal valves handle both.
Replace if needed
If the valve is cracked or still fails, replace it — see our fill valve guide.
