What you need to do before you start

A sink strainer is the basket that sits in the drain opening and catches food and debris. When it cracks, rusts, or stops sealing properly, water leaks under the sink. Replacing one takes about 30 minutes and costs $10 to $30 for the strainer itself — no plumber needed.

Before you begin, turn off the water supply under the sink by turning the shutoff valves clockwise. If your sink has no shutoff valves, you can work without turning off the main water, but you will get wet when you disconnect the drain pipes. Place a bucket under the P-trap (the curved pipe below the drain) to catch standing water.

Gather these tools: an adjustable wrench, a screwdriver, a putty knife, plumber's putty or silicone caulk, and a flashlight. Have a towel nearby. The strainer itself comes as a complete assembly — basket, flange (the ring that sits on top), and locknut (the ring underneath that holds it in place).

Key Takeaways

  • You must disconnect the P-trap and remove the locknut from underneath the sink before the old strainer will come out.
  • The new strainer needs plumber's putty or silicone caulk around its base to seal it and prevent leaks under the sink.
  • Hand-tighten the locknut first, then use a wrench to snug it — over-tightening cracks the flange and causes leaks.
  • Reconnect the P-trap and test for leaks by running water for 30 seconds and checking underneath.

Disconnect the P-trap and drain lines

Slide under the sink with your flashlight. Locate the P-trap — the curved section of pipe directly below the drain opening. At both ends of the P-trap, you will see slip nuts (large nuts that hand-tighten). Use your adjustable wrench to loosen the slip nut on the tailpiece (the straight pipe coming down from the sink) first, then loosen the slip nut on the wall drain (the pipe going into the wall or floor).

Once both nuts are loose, unscrew them by hand and pull the P-trap straight down. Water will spill into your bucket. If your sink has a garbage disposal, the process is the same — the P-trap connects the same way. Set the P-trap aside on a towel.

If your sink has a pop-up stopper (the plug that opens and closes), you may see a rod connected to it under the sink. You do not need to disconnect it — it will stay in place while you work on the strainer.

Remove the old strainer from above and below

From above the sink, look at the strainer basket. You may see a set screw or clip holding it in place — if so, remove it with a screwdriver. If there is no screw, the basket is held only by the locknut underneath.

Slide underneath again. You will see the locknut — a large ring directly under the drain opening. Use your adjustable wrench to turn it counterclockwise. It will take some force the first few turns. Once it is loose enough, unscrew it by hand and set it aside. The old strainer will now lift out from above. Use your putty knife to scrape away all the old putty or caulk around the drain opening — this must be completely clean before the new strainer goes in.

Install the new strainer with putty or caulk

Roll a rope of plumber's putty about the thickness of a pencil and press it around the underside of the new strainer's flange (the ring that sits on top). If you are using silicone caulk instead, explore a bead around the underside of the flange. Putty is easier to remove later if you need to adjust the strainer; caulk is more durable and works better on stainless steel sinks.

Lower the new strainer into the drain opening from above. Press down firmly so the putty or caulk spreads evenly and the flange sits flat against the sink. Excess putty will squeeze out around the edges — that is normal and means you have a good seal.

Slide underneath and thread the locknut onto the strainer by hand. Once it is hand-tight, use your wrench to turn it clockwise another quarter-turn. Stop there. The most common mistake is over-tightening, which cracks the flange and causes leaks. You want it snug, not cranked down.

Reconnect the P-trap and test

Slide the P-trap back into position. The tailpiece (from the sink) goes into the top opening, and the wall drain goes into the bottom opening. Hand-tighten both slip nuts, then use your wrench to snug each one another quarter-turn. Again, snug is the goal — over-tightening can crack the nuts and fittings.

Turn the water back on and run water into the sink for 30 seconds. Watch underneath for drips at the locknut, at both slip nuts, and where the P-trap connects. A few drops during the first few seconds are normal as air escapes. If water streams out or drips continue after 30 seconds, turn off the water and tighten the leaking connection another quarter-turn.

Once the sink drains without leaking, wipe away any excess putty from around the flange with a damp cloth. If you used caulk, let it cure for 24 hours before running hot water through the sink.

Troubleshooting common problems

If water leaks from under the flange (where the strainer meets the sink), the putty or caulk did not seal properly. Turn off the water, remove the locknut, lift out the strainer, and scrape away all the old putty. Start over with fresh putty, pressing it firmly around the flange before reinstalling.

If the locknut leaks, it may be cracked or the rubber washer inside may be damaged. Most replacement strainers come with a new washer, but if yours did not, you can buy a washer separately for a few dollars. Remove the locknut, replace the washer, and reinstall.

If water leaks from the slip nuts on the P-trap, the rubber washers inside those nuts may be worn. These washers are inexpensive and available at any hardware store. Loosen the slip nut, remove the old washer, install a new one, and tighten again.

Frequently Asked Questions

Do I need to turn off the water to replace a strainer?

No, but you will get soaked when you disconnect the P-trap because standing water will pour out. Turning off the water at the shutoff valves under the sink keeps you dry and makes the job faster. If your sink has no shutoff valves, you can still replace the strainer — just have a bucket ready.

What is the difference between plumber's putty and silicone caulk?

Plumber's putty is softer, easier to remove, and works on most sinks. Silicone caulk is waterproof, lasts longer, and works better on stainless steel and composite sinks where putty can stain. Both seal the strainer equally well if applied correctly.

How tight should the locknut be?

Hand-tight plus one quarter-turn with a wrench. Over-tightening cracks the flange and causes leaks. If you hear a cracking sound or feel sudden resistance, stop when ready — you have gone too far.

Can I replace a strainer on a double sink?

Yes, the process is identical for each drain. If both strainers need replacing, do one at a time so you do not lose track of which P-trap belongs to which side. Each side has its own P-trap and locknut.

What if the old strainer is stuck and will not come out?

explore penetrating oil (like WD-40) around the locknut and let it sit for 15 minutes. Try loosening it again with your wrench. If it is still stuck, tap the wrench handle gently with a hammer to break the corrosion loose, then try again. Do not force it — you risk cracking the sink.