2. Reseal a leaky strainer

The primary seal around a basket strainer is plumber’s putty, which doesn’t last forever. Over the years it can harden, shrink or crack. Sometimes you can stop a leak by tightening the locknut. But in many cases, the only cure is a new dose of putty.

Photos 1 – 4 below show you how. You can reuse the old strainer if all the parts are in good shape, but it usually makes sense to replace it. Expect to spend at least $15—cheaper strainers are less reliable. Since you have to take apart most of the drain assembly to get at a leaking strainer ( Photo 1), consider replacing the drain lines if they’re old (see p. 50).

The hardest part of this job is unscrewing the old locknut, which is often welded in place by mineral deposits or corrosion. A special wrench designed just for locknuts, called a “spud wrench” or “locknut wrench” ( Photo 2), costs about $15. Big slip-joint pliers ($25) with a 3-1/2-in. jaw opening will work too, plus you can use them for other jobs. Whatever tool you use, you might find that the locknut won’t budge. In that case, a single cut with a hacksaw blade is the only solution ( Photo 3). It’s almost impossible to do this without cutting into the strainer threads, so plan on buying a new strainer.

With the locknut removed, pull out the strainer and scrape old putty off the sink with a plastic putty knife. Installing a new strainer is simple ( Photo 4). Just remember that the rubber washer goes on before the cardboard washer. Tighten the strainer using the same method you used to remove it.

Locknut Strainer Locknut wrench Turn the locknut counterclockwise to remove the strainer. Have a helper stick the handles of the pliers into the strainer holes and keep the strainer from turning using a screwdriver.

Plumber’s putty Encircle the drain opening with plumber’s putty or waterproof caulk. Install the rubber washer and the cardboard washer and tighten the locknut using the same method you used to remove the old one.

Slip nut Leaky strainer Disassemble the drain assembly so you can remove the leaky strainer. Turn slip nuts counterclockwise, using a second set of pliers if necessary to keep the pipes from turning.

Stubborn locknut Cut the locknut with a hacksaw if you can’t unscrew it. Cut at a sharp diagonal angle and be careful not to cut into the sink.