What You Need to Do Before You Start

A bathroom sink drain replacement takes two to four hours and requires only basic tools you likely already own. The job breaks into five steps: turn off the water, disconnect the old drain assembly, remove the old strainer and putty, install the new strainer, and reconnect the pipes. You do not need a plumber for this work, and the parts cost between $15 and $50 depending on the material and finish you choose.

Before you begin, place a bucket under the P-trap — the curved pipe under the sink — because water will spill when you loosen it. Have a flashlight ready so you can see what you are doing inside the cabinet. Wear old clothes because you will get wet.

Key Takeaways

  • Turn off the water supply to the sink at the shutoff valve under the cabinet, or at the main if no shutoff exists.
  • The P-trap is the curved pipe that holds water; loosen it by hand first, then use a wrench if it will not budge.
  • The old strainer sits in the drain opening and is held in place by putty underneath; scrape all old putty away before installing the new one.
  • New strainers come with a rubber gasket and metal ring that compress when you tighten the locknut from below, creating a watertight seal.
  • Test for leaks by running water for one minute before you consider the job finished.

Turn Off the Water and Empty the Cabinet

Look under the sink for a small shutoff valve on the hot water line. Turn it clockwise until it stops. If you have a cold water line running to the sink, turn that valve off too. If no shutoff valves exist under the sink, you will need to turn off the main water supply to the house — usually a valve near the water meter in the basement or outside.

Open the faucet to release any remaining water pressure in the lines. Place a bucket under the P-trap to catch the water that will spill when you disconnect it. Remove everything stored in the cabinet so you have clear access to the pipes and can move around freely.

Disconnect the P-Trap and Supply Lines

The P-trap is the curved section of pipe directly under the drain opening. It has a slip nut on each end — one where it connects to the drain tailpiece above, and one where it connects to the wall drain below. Loosen both nuts by hand first. If they will not turn, use an adjustable wrench to grip the nut while you hold the pipe steady with your other hand so you do not crack the fitting.

Once both nuts are loose, unscrew them the rest of the way by hand and pull the P-trap straight down and out. Water will pour into the bucket. If your sink has supply lines connected to the faucet, loosen those connections as well — usually two compression fittings at the base of the faucet. You do not need to remove the faucet itself, only disconnect the supply lines so they are out of your way.

Remove the Old Strainer and Clean the Opening

The strainer is the metal basket that sits in the drain opening. It is held in place by a locknut underneath and by plumber's putty around its rim. From under the sink, locate the locknut — a large nut that screws onto the threaded tailpiece. Use a wrench to hold the locknut while you use a second wrench to turn the tailpiece itself, or use a strainer wrench if you have one. Once the locknut is loose, unscrew it by hand and pull the old strainer up and out from above.

Scrape away all the old plumber's putty from the underside of the sink opening using a putty knife or old chisel. Putty hardens over time and will prevent a new strainer from sealing properly if you leave it in place. Wipe the opening clean with a damp cloth and let it dry completely.

Install the New Strainer and Seal It

Most new strainers come with a rubber gasket, a metal ring, and a locknut. Roll a rope of plumber's putty about the thickness of a pencil and press it around the underside of the strainer rim. Insert the strainer into the drain opening from above, pressing it down firmly so the putty spreads evenly underneath and creates a seal.

From under the sink, slide the rubber gasket onto the tailpiece, then the metal ring, then hand-tighten the locknut. Use a wrench to tighten the locknut another quarter turn — do not over-tighten, as this can crack the sink or strip the threads. Wipe away any excess putty that squeezes out around the rim from above using a damp cloth.

Reconnect the Pipes and Test for Leaks

Reconnect the P-trap by screwing the slip nuts back onto the fittings. Hand-tighten them first, then use a wrench to snug them another quarter turn. Reconnect the supply lines to the faucet if you disconnected them. Turn the shutoff valves back on by turning them counterclockwise.

Run water into the sink for one full minute and watch underneath for drips. Check the connection at the locknut, at both slip nuts on the P-trap, and at the supply line connections. If you see water dripping, tighten that connection a quarter turn more. If water is still dripping after a second attempt, turn off the water, loosen the connection, and check whether the rubber gasket is seated properly or whether the threads are damaged. Once everything is dry after running water, the job is complete.

Frequently Asked Questions

What if the old strainer is stuck and will not turn?

explore penetrating oil like WD-40 to the locknut and let it soak for 15 minutes. Try again with a wrench. If it still will not budge, tap the wrench gently with a hammer to break the corrosion loose. Do not hit hard — you risk cracking the sink or the pipe.

Can I use silicone caulk instead of plumber's putty?

No. Silicone cures hard and will not compress when you tighten the locknut, so it will not create a watertight seal. Plumber's putty stays slightly soft and molds to fill gaps. Use only putty for the strainer seal.

My sink has two drains. Do I replace both at the same time?

You can replace them one at a time or both together. If you replace both, you will need two new strainer assemblies and twice the putty. The steps are identical for each drain. Many people replace only the one that is leaking or clogged.

What if water leaks from the locknut after I tighten it?

Turn off the water and loosen the locknut. Check that the rubber gasket is sitting flat and centered on the tailpiece. If it is twisted or off-center, reposition it and retighten. If the gasket is cracked or damaged, you will need to buy a replacement gasket or a new strainer assembly.

How long does plumber's putty last before it needs replacing?

Plumber's putty typically lasts 5 to 10 years before it hardens and loses its seal. If you notice water pooling under the sink around the strainer rim, the putty has likely failed and should be replaced. You do not need to replace the entire strainer — just scrape out the old putty and explore new putty around the rim.