How to Replace a Leaking P-Trap Under Your Bathroom Sink

A leaking P-trap is one of those problems that looks worse than it actually is. The P-trap—that U-shaped pipe under your sink—traps water to create a seal that prevents sewer gases from backing up into your home. When it leaks, you get water pooling in your cabinet, mold starting to grow, and that sinking feeling that plumbing repair means calling someone expensive. But replacing a P-trap is genuinely a beginner job. The connections are hand-tight, the parts cost under thirty dollars, and once you understand the three-connection system, you're already most of the way there. What 'done well' looks like: a new trap that connects without stripping threads, drains smoothly, and stays dry under the sink for months to come.

1. Clear the Workspace First. Turn off the water supply valve under the sink. If there's no shutoff valve, go to the main water shutoff in your home. Next, pull everything out of the cabinet under the sink—cleaning supplies, plumbing parts, the collection of things you've been meaning to deal with. Wipe down the cabinet floor with a towel to see what you're working with. Place a bucket directly under the P-trap to catch residual water when you disconnect it.
2. Identify All Three Connections. Look at the pipe coming down from your sink drain. It connects to the top of the P-trap (the tailpiece connection). The P-trap itself is the U-shaped section. At the bottom, where the P-trap angles back toward the wall, it connects to the wall drain line (the second connection). The third connection is where the overflow tube from the sink basin meets the P-trap side arm. You'll see two large slip nuts—one at the top where the tailpiece connects, one where the P-trap meets the wall drain. These are what you'll unscrew.
3. Release the Top Connection. Using an adjustable wrench or slip-nut wrench, grip the slip nut (not the pipe itself) and turn counterclockwise. The tailpiece is the vertical pipe coming down from the sink drain opening. Turn slowly to break the seal, then unscrew by hand. As you unscrew, steady the tailpiece with your other hand so you don't stress the sink connection above. Once loose, set the nut aside and gently pull the tailpiece slightly upward to separate it from the P-trap.
4. Free the Bottom Connection. Now work on the lower connection where the P-trap meets the wall drain line. Using your wrench, grip the slip nut where the P-trap exits and turns toward the wall. Turn counterclockwise, again turning the nut, not the pipe. Once the nut breaks free, unscrew it by hand and set it aside. You may need to twist the P-trap slightly to wiggle it free from the wall drain fitting. Place your bucket directly under this joint as you separate it—this is where the pooled water inside the trap will spill.
5. Unhook the Overflow Tube. Look at the side of the P-trap. Many bathroom sinks have an overflow tube that runs from the basin down to connect to the P-trap's side arm. This connection is usually a simple compression fitting or clamp. If it exists, loosen the compression nut by turning it counterclockwise, or loosen any hose clamp with a screwdriver. Gently separate the overflow tube from the P-trap side arm. If there's no overflow tube, skip this step.
6. Extract and Clean Thoroughly. With both slip nuts loosened and the overflow tube (if any) disconnected, the P-trap should lift out freely. Carry it to your bucket or sink to dispose of any remaining water inside. Look at the wall drain opening where the P-trap was connected. Use an old cloth or paper towel to wipe away debris, mineral buildup, or old plumber's grease around the threads. This is critical—any debris left behind will prevent a watertight seal with your new trap.
7. Grease the Connection Points. With the old trap removed, look at the tailpiece coming down from your sink. This is the vertical pipe that was connected to the top of the P-trap. If there's buildup or mineral deposits around the threads at the bottom, wipe it clean with a cloth. Apply a thin layer of plumber's grease (also called silicone grease or Vaseline) to the threads of both the tailpiece and the wall drain opening. This helps the new trap seal properly and makes future removals easier.
8. Seat the Top Connection. Take your new P-trap and position it under the sink so the top opening aligns with the tailpiece coming down from the sink. Thread the slip nut onto the tailpiece first by hand—start the threads manually so you don't cross-thread. Once hand-tight, use your wrench to snug it down. Turn the slip nut until it's snug and the P-trap is held in place, but don't overtighten. You're aiming for 'hand-tight plus a quarter turn'—tight enough that it won't leak, not so tight you strip the threads.
9. Secure the Bottom Connection. Now work on the lower connection. Position the exit end of the P-trap so it aligns with the wall drain opening. The angle should be natural—the P-trap should sit without twisting or straining. Thread the slip nut onto the wall drain threads by hand, starting slowly to ensure proper engagement. Once hand-tight, use your wrench to snug it down with the same quarter-turn rule. The P-trap should now be fully supported by both connections.
10. Reattach the Overflow Tube. If your sink has an overflow tube, reconnect it to the side arm of the new P-trap at the same location where it was connected on the old trap. Hand-tighten the compression fitting or tighten the hose clamp with a screwdriver. Don't over-torque this connection—it's just a compression fitting and can be overtightened easily. The tube should be snug enough that it won't slip off under water pressure.
11. Check for Leaks Immediately. Go back to the shutoff valve under the sink and turn the water back on slowly. Return to the cabinet and watch the P-trap connections for any dripping. Run the sink at moderate flow for thirty seconds and observe both the tailpiece connection at the top and the wall drain connection at the bottom. Also fill the sink basin and let it drain to ensure water flows through the P-trap properly. Check for any water pooling on the cabinet floor.
12. Monitor and Verify Success. Wipe the cabinet floor completely dry with a towel. Leave the cabinet doors open to allow air circulation. Before you call this job complete, check back in an hour and again the next morning. Most P-trap leaks show themselves within the first few hours. If the cabinet floor is bone dry, you're done.