Toilet Leaking Between Cistern and Pan

Confirm the leak location — dry the joint between cistern and pan and flush. If water immediately appears at the join, it is the flush seal. If water runs down the pan from higher up, check the overflow or fill valve instead.

Turn off the water supply at the isolation valve. Flush to empty the cistern. Use a sponge or towel to remove any remaining water from the cistern.

For close-coupled toilets (cistern sits directly on pan): undo the two bolts on the underside of the cistern (usually accessed from inside the cistern — remove the lid and look for two wing nuts or hex nuts). Support the cistern before removing the second bolt.

Lift the cistern away and inspect the close-coupled washer (the large rubber ring between cistern and pan). It will likely be flattened, cracked, or perished. Take it to a plumbing merchant to match the size — they are not universal.

Fit the new washer, lower the cistern back into position, and hand-tighten the bolts. Do not overtighten — over-torquing cracks the ceramic cistern.

Turn the water back on, allow the cistern to fill, and flush several times. Watch the joint carefully for any drips.

If the toilet is low-level (cistern connected via a flush pipe with a push-fit or spigot connection), the seal is at each end of the flush pipe — replace the rubber cone washers at each connection point.