What You Need to Know Before You Start

A kitchen sink drain replacement takes about 30 to 45 minutes if you are working with a standard P-trap setup under a single-bowl sink. You will need a bucket, two adjustable wrenches, plumber's putty, and a new drain assembly that matches your sink's opening size — typically 3.5 inches in diameter. The job involves disconnecting the old drain from underneath the sink, removing it from above, and installing the new one in reverse order.

The most common mistake is forgetting to place a bucket under the trap before loosening it. Even if you think the pipes are dry, there is always standing water. The second mistake is over-tightening the new connections — hand-tight plus a quarter turn with a wrench is enough. Over-tightening cracks the plastic fittings or strips the threads on metal ones.

Key Takeaways

  • Place a bucket under the P-trap before you loosen anything, because water will spill even from pipes that look empty.
  • The drain assembly comes in two parts — the strainer basket that sits in the sink opening, and the tailpiece that hangs below — and both must be removed and replaced.
  • Plumber's putty seals the strainer basket to the sink from above and prevents water from leaking around the rim.
  • Hand-tighten all connections first, then use a wrench for a quarter turn; over-tightening breaks plastic fittings and strips metal threads.
  • Test for leaks by running water for 30 seconds and checking all connections from underneath before you consider the job done.

Gather Your Tools and Materials

You will need two adjustable wrenches — one to hold the nut steady while the other turns it. A bucket or shallow pan catches the water that drains from the trap. Plumber's putty is a clay-like sealant that comes in a roll; it costs a few dollars and lasts for years. You also need a new drain assembly, which you can buy at any hardware store for $15 to $40 depending on material and finish.

Before you buy the new drain, measure your sink opening from the rim. Most kitchen sinks use a 3.5-inch opening, but some older or specialty sinks use 2.5 inches or 4 inches. Bring a tape measure or a photo of your sink to the store. The drain assembly should include the strainer basket, the tailpiece (the vertical pipe below), and rubber washers and nuts. If it does not, buy them separately — they cost $2 to $5.

Remove the Old Drain from Underneath

Slide under the sink and locate the P-trap — the U-shaped pipe. Place your bucket directly underneath it. Using one wrench to hold the nut on the vertical section and the other to turn the nut on the horizontal section, loosen the connection where they meet. Turn counterclockwise. Water will drain into the bucket. Once the trap is loose, you can unscrew it by hand and set it aside.

Now locate where the tailpiece (the straight pipe coming down from the sink) connects to the trap. Loosen this nut the same way — one wrench holding, one turning. Once loose, unscrew by hand. The tailpiece should now hang freely. Look up into the sink and you will see the strainer basket sitting in the opening. From underneath, there is a large nut holding it in place. This is called the locknut. Use your wrench to turn it counterclockwise. It will be tight; do not be afraid to explore steady pressure.

Remove the Old Strainer Basket from Above

Once the locknut is loose enough to turn by hand, unscrew it completely and set it aside. The strainer basket will now lift out of the sink from above. There will be old plumber's putty around the rim — scrape it away with a putty knife or old butter knife. Get the sink rim completely clean and dry. Any old putty left behind will prevent the new strainer from sealing properly.

Wipe the rim with a dry cloth. If there is any grease or residue, use a cloth dampened with rubbing alcohol and dry it again. The rim must be clean for the new putty to stick.

Install the New Strainer Basket

Roll a rope of plumber's putty about the thickness of a pencil and press it around the underside of the new strainer basket's rim — the part that will sit against the sink. You need enough to form a complete seal, but not so much that it squeezes out everywhere when you press down. A circle about 3 inches in diameter is usually right.

Lower the strainer basket into the sink opening from above. Press down firmly so the putty compresses and creates a seal. From underneath, thread the rubber washer onto the locknut, then thread the locknut onto the strainer's threaded post. Hand-tighten it first. Once it is snug, use your wrench to turn it another quarter turn — no more. Wipe away any putty that squeezed out around the rim with a damp cloth.

Reconnect the Tailpiece and Trap

The tailpiece is the straight pipe that hangs from the strainer basket. Thread the rubber washer and nut onto the bottom of the tailpiece, then thread it onto the strainer's post underneath the sink. Hand-tighten, then use your wrench for a quarter turn. Do not over-tighten.

Now reconnect the P-trap. The trap has two ends — one connects to the tailpiece, the other to the wall drain. Slide the rubber washer and nut onto the tailpiece end first, then thread it onto the tailpiece. Hand-tighten and then quarter-turn with the wrench. Slide the washer and nut onto the wall drain end and thread it on the same way. Hand-tighten and quarter-turn. All three connections — strainer to tailpiece, tailpiece to trap, trap to wall — should now be snug but not cranked down.

Test for Leaks

Fill the sink with water and let it drain completely while you watch from underneath. Look at all three connection points. Water should not drip from any of them. If you see a drip, tighten that nut by a quarter turn and test again. If water is still dripping after a second quarter turn, turn off the water, loosen the nut, check that the rubber washer is seated properly, and tighten again.

Run the water for 30 seconds and check one more time. If everything is dry, you are done. If water pools in the bucket, do not use the sink until you have found and fixed the leak. The most common cause is a washer that is not seated flat or a connection that was not tightened enough.

Frequently Asked Questions

Can I replace just the strainer basket without replacing the whole drain?

Yes, if the tailpiece and trap are in good condition. You only need to remove the locknut, lift out the old basket, scrape away the putty, and install the new basket the same way. This takes about 10 minutes and costs $5 to $15 for just the basket.

What if the locknut is stuck and will not turn?

Spray it with penetrating oil like WD-40 and wait 15 minutes. Then try again with your wrench. If it still will not budge, wrap a cloth around the nut to protect your hand and tap it gently with a hammer to break the corrosion, then try turning it. Do not hit hard — you are loosening it, not breaking it.

Do I need plumber's putty or can I use caulk instead?

Plumber's putty is better because it stays pliable and does not harden. Caulk hardens and can crack, allowing water to seep through. If you use caulk, you will have to scrape it all away and start over the next time you need to remove the strainer. Putty costs less and lasts longer.

How do I know if my new drain assembly is the right size?

The strainer basket opening should fit snugly into your sink's drain hole with just a tiny bit of wiggle room. If it is too small, water will leak around the edges. If it is too large, it will not fit at all. Most standard kitchen sinks use 3.5 inches, but measure your old basket before you buy the new one.

What if water leaks from the connection where the tailpiece meets the wall drain?

This usually means the rubber washer is not seated flat or the nut is not tight enough. Loosen the nut, pull the tailpiece out slightly, check that the washer is flat and not twisted, push the tailpiece back in, and tighten the nut again. If it still leaks, the wall drain fitting may be damaged and you may need to call a plumber.