The kitchen sink flange is the ring that connects the drain opening in the sink to the drainpipe or garbage disposal unit below. Most people give the flange little thought, as in many cases it appears to be a solid piece or a continuation of the sink itself. This isn't the case, though. The flange is sealed to the pipe or disposal. If it fails, you will end up with a leak.
Signs of a Leaking Flange
The first sign that the flange is leaking is usually discovering water in the cabinet beneath the sink. Inspect the pipes and garbage disposal carefully to pinpoint the source of the leak. If the only dampness is located on the bottom of the garbage disposal or at a pipe joint, then the issue isn't the flange. On the other hand, if you trace the moisture to the top of the garbage disposal or where the drain pipe connects to the sink, then the flange is the likely culprit. From above and inside the sink you may also notice that the flange ring around the drain seems loose, or there may be visible peeling of the silicone caulk.
Causes of a Sink Flange Leak
The most likely culprit if you have a garbage disposal is the gasket ring that connects the flange to the disposal unit. Over time this gasket dries out and begins to crack, thus resulting in a leak. If the gasket is still in good condition or if you don't have a disposal unit, then the problem is likely with the silicone caulk that is used to seal the connection between the flange and the sink itself. Much like a gasket, this can eventually wear out and begin to degrade.
Flange Repair Options
Fortunately, a leaking flange is a relatively simple repair. For failed flange gaskets, all you need to do is purchase the correct size replacement. Cut power to the garbage disposal unit and then disconnect it from the drain flange. Remove the old gasket and swap out the new before reattaching everything. Set a bucket beneath the sink and run some water to test for leaks. If the flange gasket is seated correctly, the leak will be solved.
If the silicone caulk has failed, you will need to strip out the remaining caulk and remove the flange. Clean the area well to remove any residue that has built up between the flange and the drain opening before running a bead of fresh caulk and replacing the flange. Allow the caulk to cure for 24 to 48 hours before leak testing or using the sink.
Contact a plumbing repair contractor if you need more help with the sink flange in your kitchen.