The ceramic cistern for my toilet has a crack in it (sorry, tried to attach a photo but it was rejected as too large: the crack is from the hole that the down pipe to the toilet bowl goes into and it's a couple of inches long.) Previously I've mended it with No Nonsense clear silicone applied from the outside edges of the rubber seal washer to beyond the end of the crack and it's lasted about three years, but it's now leaking again. I've now removed the old silicone as best I can and I'm going to try sealing it again.
My question is: Is there anything that would work better than silicone sealant (e.g. plumber's mait)? Thanks.