Richard Trethewey diagnoses and offers tips to sealing leaky rubber gaskets
I replaced my kitchen sink drains using the rubber gaskets provided, and had to retighten them three times in two days to stop the leaking. Should I have used plumber’s putty?
—Joseph Hurd, Shelby, NC
In a word, yes. The gasket on a sink’s basket-strainer assembly cushions the top edge of the strainer’s bell—the shiny piece in my right hand, above—or a friction ring under the sink. But the only way to make a waterproof seal between the strainer and the top side of the sink’s hole is by using plumber’s putty.
When properly installed, this concoction of powdered limestone and oils or polymers will stop leaks for years and years in non-pressurized drain fittings. You just knead the putty in your hands briefly to make it pliable, then roll it into a snake about a half-inch across. Loop the snake around the underside of the strainer’s flange, overlapping the ends slightly, and push the strainer down through the sink’s hole and against its basin.
Now go underneath, place the gasket and the bell or ring against the underside of the sink, and thread on the locknut. Stick a couple of screwdrivers into the strainer and get a helper to hold on to them; that will keep the strainer from turning as you use pump pliers to tighten the locknut. Continue tightening until the strainer’s flange is tight against the sink and the excess putty has oozed out into the sink. Finish connecting the drainpipe to each strainer, then collect the excess putty and put it back into the container for your next sink-drain project.
There’s no need to wait for the putty to set; you can use the sink right away. But first, test for leaks by filling the sink partway with water. If there aren’t any drips before or after you let the water out, your sink should be leak-free and should remain so indefinitely.
Shown: Richard Trethewey takes apart a new basket strainer for a kitchen sink as he prepares to replace one that’s corroded and leaking.