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. Browse the full toilet cistern range for compatible parts.