3. If the pipes are old, replace the whole works
Some leaks can’t be stopped with straightening or tightening. Stripped nuts won’t tighten and old washers won’t seal because they’re stiff and distorted. You could get new nuts, washers or drain parts. Since plastic pipe is so inexpensive and easy to install, the smart, reliable fix is a whole new drain assembly. You can buy everything you need at home centers for about $20. Kits for side outlet assemblies (like the one shown here) or center outlet assemblies (where the trap is beneath the center of the sink) contain most of the essential parts.
But you might also need:
Long tailpieces (Photo 1). The tailpieces that come with kits are often only a couple of inches long.
A trap arm extender (Photo 2).
The arm that comes with the kit may not reach the drainpipe that protrudes from the wall.
A dishwasher wye that has a connection for your dishwasher hose. A disposer kit that allows the waste arm to connect to a garbage disposer.
Strainer Rubber washerCardboard washer LocknutTailpiece washer Tailpiece Tailpiece washer Slip nut Attach the tailpiece to the basket strainer, but don’t fully tighten it yet; you’ll have to remove and cut it later. Waste arm Tailpiece Trap arm Extender 1-1/2" adapter Slide the trap arm into the adapter. Then attach the trap and slide the arm in or out to position the trap directly under the tailpiece. You may need to cut the arm or add an extender. Waste tee 1-1/2" Tailpiece Trap Hold the waste tee alongside the tailpiece about 1-1/2 in. below the top of the trap. Mark the tailpiece 1/2 in. below the top of the tee. Cut both tailpieces to the same length and install them.