Replace a Bathroom Sink Drain

Replacing a bathroom sink drain is one of those jobs that looks more intimidating than it actually is. The drain assembly sits right in front of you under the sink, held in place with a few bolts and a compression fitting. Whether your drain is leaking, corroded, or you're just upgrading to a better-looking pop-up mechanism, the process is the same: disconnect the plumbing, remove the old drain body, and install the new one. Most people finish this in under an hour, and you'll save the $150 to $300 a plumber would charge for the service call. The hardest part is usually just reaching into the tight space under the sink—but a headlamp and some patience handle that.

1. Cut Off Water, Clear Space. Close the shutoff valves under the sink by turning the handles clockwise. If there are no shutoff valves, turn off the main water supply. Empty everything from the cabinet below the sink so you have clear access. Place a bucket or shallow pan on the floor directly beneath the P-trap—it will catch residual water when you disconnect the drain.
2. Free the P-Trap. Using a wrench or adjustable pliers, loosen the compression nut at the bottom of the P-trap where it connects to the wall drain. Turn it counterclockwise until hand-tight, then unscrew it fully by hand. Do the same for the compression nut at the top of the P-trap where it connects to the drain body. Set the P-trap aside and let any trapped water drain into your bucket.
3. Unbolt the Drain Body. Look up at the underside of the sink basin. You'll see the drain body threaded through the hole, with a locknut screwed onto the threaded shaft from below. Using a basin wrench or a wrench that fits the nut, turn the locknut counterclockwise. You may need to hold the drain body steady from above (have someone help, or use a cloth to grip it) so it doesn't spin. Once the nut is loose enough, unscrew it the rest of the way by hand.
4. Pull Old Drain Out. Once the locknut is fully removed from below, the entire drain body should lift out from the sink opening above. If it's stuck, rock it gently side to side to break the seal—old plumber's putty or silicone can grip it. Set the old drain aside. Use a plastic scraper or putty knife to scrape away any remaining putty or caulk from around the drain hole in the sink. Wipe the hole clean with a dry cloth.
5. Seat New Drain Assembly. Check that your new drain assembly is complete—it should include the flange, drain body, locknut, rubber washer, and friction ring. If it came with a pop-up stopper, set that aside for now. Apply a rope of plumber's putty around the underside of the new drain flange—a piece about the size of a pencil, forming a ring. If the manufacturer specifies silicone instead of putty, use that. Press the new drain assembly through the hole in the sink basin from above, seating the flange firmly against the sink.
6. Lock Down the Flange. From under the sink, slip the rubber washer onto the drain body, then the friction ring, then hand-screw the locknut onto the threaded shaft. Tighten it firmly with your basin wrench or adjustable wrench, turning clockwise. You want it snug enough that the flange doesn't move or leak, but not so tight that you crack the sink or strip the threads. Excess putty will squeeze out around the flange—that's normal. Wipe it away immediately with a wet cloth.
7. Connect Pop-Up Linkage. If the drain is a pop-up style, insert the pop-up plug from the top of the drain and orient it so the stem points toward the overflow hole on the side of the sink basin. From below the sink, insert the popup linkage rod through the back of the drain body. Position the horizontal rod so it's parallel to the basin. Secure the rod with the set screw or clip provided. Test the pop-up by lifting and pressing the lever on the side of the sink—the plug should rise and fall freely.
8. Reattach P-Trap Fittings. Position the P-trap so its lower end connects to the wall drain stub and its upper end aligns with the drain body outlet. Hand-tighten the compression nut at the bottom first, then hand-tighten the nut at the top. Once both are hand-tight, use your wrench to snug each one—a quarter to half turn past hand-tight is usually enough. Don't over-tighten; these compression fittings don't need excessive force.
9. Verify Zero Leaks. Turn the water supply back on slowly. Fill the sink with water, then drain it while you watch under the cabinet. Check the compression nuts where the P-trap connects, the locknut where the drain enters the sink, and around the drain flange. Look for drips or slow seeping. If you see water, tighten the leaking nut a quarter turn and retest. Allow the sink to drain completely and watch for five minutes.
10. Finish and Restore Order. Once you've confirmed there are no leaks, dry the area under the sink and remove the bucket. Return cleaning supplies, toiletries, and any other items to the cabinet. If you used plumber's putty and it's still wet around the drain flange above the sink, clean it away with a damp cloth. Your new drain is now in place and ready for use.