Although you only fill a sink up to the overflow infrequently, it’s important that overflow connections are well sealed. A leaking connection will cause a great deal of mess but it’s often difficult to determine whether it’s the over-flow connection or the sink waste that’s leaking. So before you do anything, fill the sink up to the overflow outlet and check underneath to see just where the water is coming from.
1. Most modern kitchens and inset sinks have a flexible pipe leading from the overflow outlet to the waste pipe, just above the trap connection to the sink. If the leak is at the connection to the outlet in the side of the sink, take off the pipe by unscrewing the little grid inside the sink.
On some of the more recently produced kitchen sinks, the grid is incorporated in the sink itself and to undo the overflow pipe to reseal the connection, all you need to do is to unscrew the nut which the plug chain is attached to. And a few sinks don’t even have an overflow outlet.
Clean the outlet and the end of the pipe then screw the grid back in position, making sure it’s as tight as possible. If the leak is around the grid, seal it with a little silicone sealant before screwing it back.
2. When you cut the nozzle of the sealant tube, make sure the opening is not too wide. For once you apply the sealant and tighten up the grid, if you have applied too much, it will ooze out of the side of the grid and look unsightly.
3. The other point where a leak can occur is at the connection to the sink waste. This connection may push on or take the form of a collar which fits around the metal outlet from the sink. To undo the connecting nuts, you will need a large adjustable spanner.
Undo the connection and clean the joint thoroughly. Check the order in which any washers are fitted as you remove them and also check and replace any damaged ones. You can then reconnect the waste and overflow and test the connection with a sink full of water.
These joints are not under any pressure, so they should be water- tight without excessive tightening of the nuts. If the connections still leak once the joints have been cleaned and re-tightened, undo the defective joints and apply a thin squeeze of sealant before reassembling.