Why Is My Kitchen Sink Tailpiece Leaking? A Complete Fix Guide

You’re reaching under the sink for a dish towel, and your sleeve lands in a wet spot. It’s not the P-trap, and it’s not the basket strainer. It’s that vertical pipe connecting the two—the tailpiece, and it’s leaving a puddle.

A tailpiece leak is one of those annoying kitchen problems that’s actually a quick, cheap fix once you know where to look. This guide shows you the likely culprits and the best way to stop that drip for good.

TL;DR

A tailpiece leak is usually caused by a worn-out slip joint washer , a misaligned or crooked pipe that breaks the seal , a cracked or corroded metal tailpiece , or a loose slip nut. Fixing it means inspecting the parts, cleaning everything, and replacing the washer if it’s flat or cracked. If the pipe itself is damaged, a new tailpiece costs under $5 and takes about 10 minutes to install .

Key Takeaways

• The washer is often the problem: The rubber or plastic compression washer inside the slip nut wears out and loses its ability to seal .
• Alignment matters: The tailpiece needs to be straight and vertical. If it’s angled, it won’t seal correctly .
• Check for cracks: Metal tailpieces can corrode and crack over time . Replacing a cracked one is cheaper and faster than a strainer replacement .
• Don’t overtighten: A final quarter-turn with a wrench after hand-tightening is usually enough to seal the new washer without damaging the plastic nut .
• Know the size: Kitchen sinks typically use a 1 1/2-inch tailpiece washer .

The Real Causes Behind a Tailpiece Leak and How to Fix It

The tailpiece is the straight, vertical pipe that runs from the sink strainer down to the P-trap. It doesn’t move, but water flows through it every time you use the sink. When it leaks, you’ll see drips right around the slip joint nuts that connect it to the strainer or the trap. Here’s why that happens.

Why Your Tailpiece is Leaking: The Most Common Culprits

1. Worn or Failed Washer

This is the number one reason for a tailpiece leak. Inside the slip joint nut is a small washer—usually rubber or plastic—that gets compressed when you tighten the nut . This compression creates the watertight seal. Over time, these washers lose their elasticity, flatten out, or even crack. When that happens, they can’t fill the microscopic gaps anymore, and water finds its way out . Many commenters on DIY forums note that replacing this simple part often solves the leak when tightening alone doesn’t help.

2. Crooked or Misaligned Pipe

The tailpiece should be perfectly vertical. If you’ve ever bumped it while storing heavy bottles under the sink, or if it wasn’t installed straight to begin with, the connection can be forced at an angle . This prevents the slip nut and washer from seating evenly, leaving a gap on one side. One user on a DIY forum fixed this exact problem by replacing a crooked brass tailpiece with a flexible or correctly aligned plastic one .

3. Corrosion or Cracks in the Pipe

Metal tailpieces, especially brass ones, can corrode over time. In some cases, the pipe end can literally corrode away or develop stress cracks around the flange where it connects to the strainer . A cracked tailpiece will leak regardless of the condition of its washer. The good news is that a replacement tailpiece is often inexpensive .

4. Loose Slip Nut

Sometimes, the fix is as simple as tightening the connection. Vibration or thermal expansion can slowly loosen the slip nut, breaking the seal. Always try a gentle tightening before anything more involved .

5. Wrong Washer Type or Direction

Using the wrong size washer or installing it backwards can cause a persistent leak. Tailpiece washers are typically flat or flanged, while the P-trap uses beveled washers . The nut must be very tight to compress a beveled washer correctly; using a flat washer where a beveled one should be, or vice versa, will result in a leak .

How to Fix a Leaking Tailpiece: Step-by-Step

Tools and Materials You’ll Need:

• Bucket or small bowl (to catch water)
• Adjustable wrench or channel-lock pliers
• New tailpiece washer (size 1 1/2-inch for kitchen sinks)
• Plumber’s putty (if you end up needing to re-seat the strainer)
• New tailpiece (if the old one is cracked)

Step 1: Confirm the Source

Place a dry paper towel under the tailpiece connection and run some water. If the towel under the top slip nut is wet, you’ve confirmed the leak is coming from the tailpiece or strainer connection .

Step 2: Tighten First

Place a bucket underneath the pipes. Try tightening the slip nuts with a wrench by hand for a snug fit. If that stops the leak, you’re done. If not, move on to inspecting the washer.

Step 3: Inspect and Replace the Washer

1. Loosen the slip nut connecting the tailpiece to the strainer with your wrench .
2. Slide the nut down the pipe and remove the old washer .
3. Look at the washer: if it’s cracked, flattened, or hardened, it needs replacement .
4. Clean the pipe threads and the inside of the drain connection thoroughly .
5. Slide a new washer onto the tailpiece, making sure it sits against the pipe’s end .
6. Slide the slip nut up and hand-tighten it firmly, then give it a final quarter-turn with your wrench .

Step 4: Check for a Cracked Tailpiece

After removing the tailpiece, inspect it closely under good lighting. Look for hairline cracks or signs of corrosion . If you find any, take it to a hardware store for a matching replacement. You can cut the new one to the correct length with a hacksaw .

Simple Tips to Prevent Future Leaks

• Use the right washer: Make sure to use the correct type and size of washer for kitchen sinks (1 1/2-inch flat or flanged).
• Hand-tighten first: For plastic slip nuts, over-tightening is a common way to crack them. Hand-tight plus a quarter-turn is usually perfect .
• A flexible option: If your pipes are frequently misaligned, you can use a flexible flanged tailpiece that can be bent into position without stressing the connection .

When to Call a Professional Plumber

If you’ve replaced the washer and even the tailpiece itself and the leak persists, or if you notice the sink strainer is the source of the leak, you may need to call a plumber. Resetting a strainer requires removing and re-sealing it with plumber’s putty .

Frequently Asked Questions (FAQs)

1. Why is my kitchen sink tailpiece leaking?
The most common causes are a worn-out slip joint washer, a loose nut, a misaligned pipe, or a cracked tailpiece .

2. Do I need to remove the whole sink to fix the tailpiece?
No. The tailpiece is accessible from under the sink. You only need to disconnect the slip nuts connecting it to the strainer and P-trap .

3. What size washer do I need for a kitchen sink tailpiece?
Kitchen sinks typically use a 1 1/2-inch tailpiece washer. Bathroom sinks use a smaller 1 1/4-inch size .

4. Can I use plumber’s putty on the tailpiece connection?
No. The tailpiece connection uses a compression washer to create the seal. Plumber’s putty is for sealing the basket strainer to the sink basin .

5. How do I know if the leak is from the strainer or the tailpiece?
Dry everything, place paper towels under each connection, and run water. If the leak comes from the strainer flange, it needs new putty. If it comes from the nut below, the tailpiece washer is likely the issue .

References

Trusted Sources for Kitchen Sink Drain Repairs:

• Las Vegas Review-Journal – Likely Causes for Leak Under Sink
• Engineer Fix – Tailpiece Washer Replacement Guide
• Jaspector – Kitchen Drain Parts and Failure Signs
• P.I. Home Inspections – Kitchen Sink Drain Parts

Which kitchen problem do you want solved next? Share your thoughts in the comments.