Replace a Leaking P-Trap Under the Sink

P-traps fail quietly. One day you notice water pooling under the sink, or you smell that distinctive sewage-trap smell, and you know the seal has gone. The good news: this is one of the few plumbing repairs that genuinely doesn't require a license or special tools. A P-trap is just a U-shaped pipe filled with standing water that blocks sewer gases from rising back into your home. When the rubber washers inside the compression fittings wear out, or the trap itself cracks or corrodes, water leaks onto your cabinet floor. Replacing it takes less than an hour and costs almost nothing. You're not rerouting pipes or soldering copper—you're unscrewing two fittings, yanking out the old trap, and screwing in a new one. The stakes are low, the win is real, and you'll never call a plumber for this again.

1. Empty the cabinet first. Empty the cabinet under the sink completely. Move cleaning supplies, paper, storage—everything. Then position a bucket or shallow pan directly under the lowest point of the P-trap. The trap contains standing water, and when you loosen the fittings, that water will drain out.
2. Kill the water supply. Locate the shut-off valve under the sink—there should be one on each hot and cold line coming from the wall. Turn both valves clockwise until they stop. Open the faucet upstairs to confirm the water is off. You don't absolutely need to kill the main water supply for this job, but it's safer and lets you work without pressure in the lines.
3. Break the seal gently. Look where the tailpiece (the straight pipe coming down from the sink drain) meets the P-trap. You'll see a large compression nut—typically brass or chrome-plated. Using an adjustable wrench, turn it counterclockwise about a quarter turn. You're not removing it yet, just breaking the seal so water can drain. The bucket below will catch most of it.
4. Unscrew and drain. Now fully unscrew the compression nut at the sink connection by hand. The tailpiece will separate from the trap. Water will drain into your bucket. Set the nut and any washers aside somewhere safe—you'll check if they're reusable later.
5. Disconnect the wall side. At the other end of the P-trap, where it connects to the drain pipe coming from the wall, you'll see another large compression nut. Using your wrench, turn it counterclockwise to loosen. Once loose enough, unscrew it by hand and set it aside with the other hardware.
6. Pull out the old trap. The old trap should now be completely free. Pull it straight down and out. If it's stuck, gently rock it side to side, but don't force it. Dispose of it or set it aside. Now inspect the tailpiece and the drain opening for old washers, mineral buildup, or debris. Wipe the inside of both connection points clean with a rag or paper towel.
7. Check washers and hardware. Pull off the old washers from the compression nuts you just removed. They're rubber or nylon discs seated inside the nut. Most of the time they're cracked, hardened, or compressed flat. Compare them to the ones that came with your new trap. If the old nuts are still in good shape and the new trap came with washers, use the new washers and reuse the old nuts. If everything is worn, use the new hardware that came with the trap.
8. Dry-fit before tightening. Dry-fit the new trap by hand first. Slide the compression nut and washer onto the tailpiece, then screw the trap onto the wall drain opening. Don't tighten yet—just thread everything by hand until it's snug. Check that the trap is straight, that the tailpiece sits fully inside the opening, and that the wall connection is centered. The trap should hang naturally under the sink without twisting or binding.
9. Snug the sink connection. Using your adjustable wrench, tighten the compression nut at the tailpiece connection. Start with the wrench and tighten a quarter turn. Then switch to tightening by hand for another quarter turn. Stop there. The goal is snug, not gorilla-tight. Overtightening will crush the washer and can crack the fitting. You should feel solid resistance when you stop.
10. Secure the wall connection. Using your wrench, tighten the compression nut where the trap meets the wall drain. Again: a quarter turn with the wrench, then a quarter turn by hand. Stop when it's snug and solid. This connection bears less stress than the sink end, but it still needs to be watertight.
11. Run water and watch. Turn the shut-off valves back on by rotating them counterclockwise. Open the faucet and let water run for 30 seconds. Watch both compression fittings and the bottom of the trap for drips. Fill the sink and let it drain once more, watching carefully. If you see water dripping from either fitting, turn off the water and tighten that nut by another quarter turn with the wrench. Test again.
12. Dry out and restore. Once the trap has held water for a full minute with no leaks, dry the interior of the cabinet with a towel. Return your cleaning supplies and other items. Leave the cabinet door open for 30 minutes so any residual dampness evaporates. You're done.