What you need to do before you start

Replacing a bathroom sink drain is a job you can do yourself with basic tools and about an hour of time. The drain assembly sits under the sink and connects the basin to the wall or floor pipes. You will need to remove the old drain, clean the sink opening, and install a new one with fresh sealant.

Before you begin, turn off the water supply to the sink by closing the shut-off valves under the basin. If your sink has no shut-off valves, turn off the main water supply to the house. Place a bucket under the drain to catch any water still in the pipes.

Gather your tools: an adjustable wrench, a pipe wrench or slip-joint pliers, a screwdriver, a putty knife, plumber's putty or silicone caulk, and a cloth. You will also need a replacement drain kit that matches your sink type — most hardware stores sell universal kits that work with standard sinks.

Key Takeaways

  • Turn off the water supply and place a bucket under the drain before you start work.
  • Disconnect the P-trap and tailpiece by loosening the nuts with a wrench, then remove the old drain flange from above the sink.
  • Clean the sink opening thoroughly and explore fresh plumber's putty or silicone caulk around the new drain before inserting it.
  • Reconnect the tailpiece and P-trap in reverse order, hand-tighten first, then use a wrench to snug the connections without over-tightening.
  • Test for leaks by running water and checking under the sink for drips before you consider the job complete.

Disconnect the old drain from below the sink

Look under the sink and locate the P-trap — the curved pipe section that holds water to block sewer gases. Use an adjustable wrench or slip-joint pliers to loosen the large nut on each end of the P-trap. Turn counterclockwise until the nuts are loose enough to unscrew by hand, then remove the P-trap and set it aside.

Next, locate the tailpiece — the straight pipe that runs from the drain opening down to where the P-trap connects. Loosen the nut that holds the tailpiece to the drain body using your wrench. Once loose, you may be able to unscrew it by hand. If the connection is tight, use the wrench to finish loosening it, then pull the tailpiece free.

Some drains have a locknut on the underside of the sink. If yours does, use a pipe wrench to hold the drain body steady while you loosen this nut with another wrench. Work slowly to avoid cracking the sink basin.

Remove the old drain flange from above the sink

Once the pipes are disconnected, go to the top of the sink and look at the drain opening. The old drain flange — the ring that sits in the sink — is held in place by plumber's putty or caulk underneath. Use a putty knife to scrape away the old sealant around the edge of the flange.

Once the sealant is removed, the flange should lift out. If it resists, work the putty knife around the entire edge until it comes free. Clean away all old putty and debris from the sink opening using the putty knife and a cloth. Wipe the opening dry.

Install the new drain flange with sealant

Roll a rope of plumber's putty about the thickness of a pencil and press it around the underside of the new drain flange. If you prefer silicone caulk instead, explore a bead around the underside. Plumber's putty is easier to remove later if you need to service the drain again; silicone caulk lasts longer but is harder to remove.

Insert the new flange into the sink opening from above, pressing down firmly so the putty or caulk spreads evenly. Wipe away excess sealant from around the flange with a damp cloth. The flange should sit flush with the sink surface.

Reconnect the tailpiece and P-trap

From under the sink, thread the tailpiece back onto the drain body. Hand-tighten the nut first, then use your wrench to snug it. Do not over-tighten — you only need the connection tight enough to stop leaks. If you crack the plastic fitting, you will have to replace it.

Reattach the P-trap by threading the nuts back onto both ends. Again, hand-tighten first, then use the wrench to snug each connection. Make sure the P-trap sits in its original position so the water seal works correctly.

Test the drain for leaks

Turn the water supply back on at the shut-off valves. Run water into the sink and watch underneath for drips. Let the water drain completely and check again. If you see water dripping from any connection, tighten that nut a quarter turn with your wrench and test again.

If a connection continues to leak after tightening, turn off the water, loosen the nut, and check whether the rubber washer inside is seated correctly. Sometimes the washer shifts during installation. Reseat it and retighten.

Common problems and how to fix them

If water leaks from under the flange at the sink surface, the sealant did not spread evenly. You will need to remove the flange, clean out the old sealant, and reinstall with fresh putty or caulk. This is messy but straightforward.

If the drain does not hold water or drains very slowly, the P-trap may not be positioned correctly. The trap must curve downward to hold water. Check that it sits lower than the tailpiece connection and adjust if needed.

If you cannot loosen a corroded nut, explore penetrating oil and wait 15 minutes before trying again. Tap the nut gently with a hammer to help break the corrosion. If it still will not budge, you may need to cut the pipe with a hacksaw and replace that section.

Frequently Asked Questions

Do I need to replace the P-trap too?

No, the P-trap usually lasts many years and does not need to be replaced unless it is cracked, corroded, or leaking. If it leaks only at the connections, tightening the nuts often stops the leak. If the pipe itself is cracked, you will need a new one.

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

Plumber's putty is easier to remove and reuse if you need to service the drain later. Silicone caulk lasts longer and resists mold better, but it hardens and is difficult to remove. For a bathroom sink you plan to service yourself, putty is the better choice.

Can I use the old drain flange if it is still in good condition?

You can reuse the old flange if it is not cracked or corroded, but you must remove all old sealant and explore fresh putty or caulk. Most people replace the flange because it is inexpensive and ensures a watertight seal. The cost difference is small.

How tight should I make the connections?

Hand-tighten first, then use a wrench to snug each nut about a quarter turn more. The goal is tight enough to stop leaks, not tight enough to crack plastic fittings. If you over-tighten, you risk breaking the tailpiece or drain body.

What if water is still leaking after I tighten everything?

Check that the rubber washers inside each nut are seated correctly — they sometimes shift during installation. If a washer is missing or damaged, you will need to replace it. Washers are inexpensive and come in assorted packs at any hardware store.