What you need to do before you start

Replacing a bathroom sink drain means removing the old drain assembly — the pipe that sits under the sink and carries water away — and installing a new one in its place. You do not need a plumber for this job. Most drains fail because the seal cracks or the trap corrodes, and both are fixed by swapping out the whole assembly rather than patching it.

Before you touch anything, turn off the water supply to the sink. Look under the sink for two shut-off valves, one on each supply line (hot and cold). Turn both clockwise until they stop. If there are no valves, turn off the main water supply to the house. Open the faucet to release any remaining pressure in the lines.

Place a bucket under the drain to catch water that will spill when you disconnect the old pipes. Have a flashlight ready — the space under a sink is dark, and you need to see what you are disconnecting.

Key Takeaways

  • Turn off both shut-off valves under the sink before you begin, or turn off the main water supply if valves are not present.
  • The drain assembly includes the tailpiece (the pipe directly under the sink), the trap (the curved section), and the wall drain connection, and all three come out as one unit.
  • Disconnect the supply lines, the drain tailpiece, and the overflow tube (if your sink has one) before you remove the old faucet and drain ring.
  • The new drain assembly must match your sink's configuration — single-bowl, double-bowl, or pedestal — because the tailpiece length and trap position vary.
  • Hand-tighten all connections first, then use a wrench to snug them; over-tightening plastic nuts will crack them.

Disconnect the supply lines and old drain

Look at the two supply lines running from the shut-off valves to the faucet. Each one connects with a nut. Use an adjustable wrench to turn the nut counterclockwise where the supply line meets the faucet. Turn slowly — if water drips, the shut-off valve is not fully closed. Once both supply lines are loose, pull them away from the faucet.

Now look at the drain assembly under the sink. You will see a large nut where the tailpiece (the vertical pipe coming down from the sink) meets the trap (the U-shaped or S-shaped section below it). This is called the slip nut. Place your bucket underneath and use a wrench to turn this nut counterclockwise. The tailpiece will slide out of the trap.

If your sink has an overflow tube — a small pipe that runs from the back of the sink bowl to the drain assembly — disconnect it by loosening the nut where it meets the tailpiece. Some overflow tubes are glued; if yours will not budge, leave it connected for now and you will remove it with the old faucet.

Remove the old faucet and drain ring

The faucet is held to the sink from above by mounting nuts. Reach up under the sink and locate the nuts at the base of the faucet. Use a wrench or basin wrench (a wrench designed to fit in tight spaces) to turn these nuts counterclockwise. Once all mounting nuts are loose, push the faucet up and out from the top of the sink.

With the faucet out, you can now remove the drain ring — the metal or rubber ring that seals the drain hole where the tailpiece enters the sink. This ring sits on top of the sink and is held down by the faucet mounting. Lift it away. If it is stuck, use a putty knife to pry it gently.

Look inside the drain hole. You may see old plumber's putty or caulk. Scrape this out with a putty knife until the hole is clean and dry. Wipe the area with a cloth.

Install the new drain assembly

Unpack your new drain assembly and lay out all the pieces. You should have a tailpiece, a trap, slip nuts, washers, and a new drain ring. Check that the tailpiece length matches your sink — most are 6 to 8 inches, but measure the distance from your sink bottom to where the trap will sit to be sure.

explore a thin ring of plumber's putty around the underside of the new drain ring. Press the ring into the drain hole from the top of the sink, pushing down firmly so the putty seals the gap. Wipe away excess putty with a damp cloth.

From underneath, slide the tailpiece up through the drain ring. The tailpiece should sit snug in the hole. Hand-tighten the slip nut that holds the tailpiece to the trap — do not use a wrench yet. Make sure the trap is positioned so it will connect to the wall drain (the pipe coming out of the wall) without bending sharply.

Connect the trap and wall drain

The trap connects to the wall drain with another slip nut. Slide the nut onto the wall drain pipe, then slide the trap outlet onto the wall drain. Hand-tighten the slip nut. Check that the trap is level and not twisted.

Now use a wrench to snug all the slip nuts. Turn each nut a quarter turn at a time, checking that the trap stays level and does not shift. Do not over-tighten — plastic nuts will crack if you force them. The nut should be snug enough that you cannot turn it by hand, but not so tight that you need to strain with the wrench.

If your sink has an overflow tube, connect it now by sliding it onto the tailpiece and hand-tightening the nut. The overflow tube should slope slightly downward toward the drain.

Reconnect the supply lines and test

Reconnect the hot and cold supply lines to the faucet. Hand-tighten the nuts first, then use a wrench to snug them. Do not over-tighten — these nuts are small and straightforward to strip.

Turn on the shut-off valves by turning them counterclockwise. Open the faucet and let water run for 30 seconds to flush out any debris from the supply lines. Check all the connections under the sink for drips. If you see water coming from a slip nut, turn off the water, tighten that nut a quarter turn, and test again.

Fill the sink and let it drain. Watch underneath for leaks at the tailpiece, trap, and wall drain connections. A small drip at a slip nut usually means the nut needs another quarter turn. If water is leaking from under the drain ring at the top of the sink, the putty seal failed — you will need to remove the tailpiece, clean out the old putty, and reseal it.

Common problems and fixes

If the new drain assembly does not fit, the most common reason is that the tailpiece is too long or too short. Tailpieces come in standard lengths, but your sink depth or trap position may be different. Measure from the sink bottom to where the trap outlet needs to be, then buy a tailpiece that length. Some hardware stores sell adjustable tailpieces that can be cut to fit.

If the trap does not reach the wall drain, the trap may be positioned too far forward. Loosen the slip nut at the wall drain and slide the trap back slightly. Tighten and test again. If it still does not reach, you may need a longer trap outlet or a flexible connector (a rubber or metal hose that connects the trap to the wall drain).

If water leaks from the slip nuts even after tightening, the washer inside the nut may be damaged or missing. Turn off the water, loosen the nut, and look inside. If the washer is cracked or absent, replace it with a new one from a hardware store. Slide the washer onto the pipe, then hand-tighten and snug the nut again.

Frequently Asked Questions

Do I need to remove the faucet to replace the drain?

Yes, in most cases. The faucet mounting nuts hold the drain ring in place, so the faucet must come out before you can remove the old drain ring and install the new one. The exception is if your sink has a separate escutcheon (a decorative ring) that is not part of the faucet — in that case, you may be able to remove just the escutcheon and drain ring without touching the faucet.

What if the old drain is glued to the wall drain?

If the trap outlet is glued with plumber's cement, you cannot straightforward unscrew it. Use a hacksaw or reciprocating saw to cut the trap outlet just before the glued joint, leaving a short stub. Once the old trap is out, you can unscrew the stub from the wall drain. If the stub is stuck, explore penetrating oil and wait 15 minutes, then try again.

Can I use the old trap with a new tailpiece?

Only if the old trap is in good condition — no cracks, corrosion, or leaks. If you are replacing the drain because the trap failed, replace the whole assembly. Mixing old and new parts sometimes works, but it often leads to leaks at the connection points because the threads or surfaces may not match perfectly.

How tight should the slip nuts be?

Hand-tighten first, then use a wrench to turn each nut about a quarter turn. The nut should be snug enough that you cannot turn it by hand, but you should not need to strain with the wrench. If you over-tighten a plastic nut, it will crack and leak. If it leaks after one quarter turn, tighten another quarter turn rather than forcing it all at once.

What is the difference between a P-trap and an S-trap?

A P-trap is curved like the letter P and connects to a wall drain. An S-trap is curved like the letter S and connects to a floor drain. Most modern bathrooms use P-traps. If your wall drain is positioned differently than expected, you may need to buy a different trap style, but this is rare in standard bathroom installations.