Cistern inlet valve replacements fail to fit more often over entry position than any other spec — brand and price point matter less than getting bottom vs side entry right the first time.
Bottom entry
A bottom entry cistern inlet valve connects through the base of the cistern, with the supply line running up from the floor or wall behind the pan. This is the more common configuration on modern concealed and close-coupled cisterns where the water supply is routed underneath.
Side entry
A side entry cistern inlet valve connects through the side wall of the cistern instead, for supply lines that come in horizontally. Older cisterns and some specific brands use this configuration — forcing a bottom-entry valve onto a side-entry setup (or vice versa) is the fastest way to end up back on site for a second visit.
How to check before ordering
Look at where the existing supply line meets the cistern, not where the valve currently sits internally — the pipe run tells you the entry position, and it's determined by the cistern's plumbing, not a preference you can choose freely on a replacement job. If in doubt, a photo of the connection point before removal saves a return trip more often than any spec sheet.
Related reading
If the toilet is running rather than just needing a routine valve swap, see our comparison of the Caroma Quietflow vs Fluidmaster Pro45 inlet valves for which specific valve to spec once you've confirmed entry position. If it's a worn washer rather than the valve itself causing the run or trickle, see our guide to matching the right cistern washer to your toilet brand. If the stop valve behind the cistern (not the inlet valve itself) is what's playing up, see our guide to mini cistern stop valves and PEX connector kits. Browse the full toilet cistern range for compatible parts.
Frequently Asked Questions
Can I convert a side entry cistern to bottom entry?
Not without changing the supply pipework — the entry point is determined by how the line was originally run, not a valve choice you can make freely.
What happens if I order the wrong entry type?
It won't connect to the existing supply line without re-plumbing, meaning a second trip and the original valve going to waste.
Are bottom entry valves more common than side entry?
Yes — most modern concealed and close-coupled cisterns use bottom entry, but plenty of older or specific-brand cisterns still use side entry, so it always pays to check rather than assume.
Does entry type affect the valve's performance or lifespan?
No — entry position is purely about how the valve connects to your existing pipework, not a performance or durability factor.