How to Choose a Toilet Fill Valve: Side vs Bottom Entry
A toilet fill valve controls the refill of the cistern after flushing. Before ordering a replacement, check where the water supply enters, the inlet thread, the available height and the clearance around the float and flush mechanism.
Side-entry or bottom-entry?
Side-entry fill valve
The inlet passes through the side wall of the cistern. Check which side the supply enters, the thread size and whether the float can move without touching the cistern or flush mechanism.
Bottom-entry fill valve
The inlet passes through the base of the cistern. Measure the internal height and check access below the cistern for the supply connection and retaining nut.
Five checks before ordering
- Entry position: side or bottom.
- Inlet connection: confirm the thread and adjoining supply connection.
- Valve height: check fixed or adjustable dimensions against the cistern.
- Float clearance: allow free movement without contacting other components.
- Fault diagnosis: confirm the fill valve is the failed part rather than a flush-valve seal or incorrect water-level setting.
What if the toilet keeps filling?
Possible causes include a fill valve that does not shut off, debris affecting the valve, an incorrectly adjusted water level or water escaping through the flush valve. Identify the source before replacing parts.
Shop replacement fill valves
Browse toilet fill valves for current side-entry, bottom-entry and height-adjustable options. For related seals, flush valves and cistern parts, see toilet spares.
Always compare the live product dimensions and connection details with the existing installation before ordering.