Toilet flapper fine — keep refill tube above waterline

A good toilet flapper seal is not the whole story. The small refill tube that tops off the bowl must clip to the overflow above the tank waterline — an anti-siphon habit that stops sneaky siphoning.

Anti-siphon refill tube above the waterline

1. Lift the tank lid. Confirm the flapper seats flat and the chain has slight slack (not lifting the flapper).
2. Find the thin refill tube from the fill valve to the overflow pipe.
3. Clip or seat the tube so its end stays above the normal waterline inside the overflow. Do not shove it down into the water.
4. Flush once. Water should refill the bowl through the overflow without the tube gulping underwater. If the tank still slowly drops with a seated flapper, revisit the flapper seal or fill-valve height — not a longer submerged tube.

Never remove the overflow tube or disable anti-siphon parts to “quiet” the tank.

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