How to Replace a P-Trap Under Your Kitchen Sink

Plumbing under a sink looks complicated until you realize the P-trap is just two pieces of pipe held together by hand-tight nuts. That U-shaped section isn't there for decoration—it holds water that seals out sewer gas and odors. When yours leaks, clogs constantly, or corrodes, replacement is a straightforward fix you can do yourself. A new P-trap costs $15 to $30, and you'll finish before lunch. The key is understanding that you're not dealing with pressurized water lines here; everything disconnects by hand or with one wrench. The trap sits right under the sink between the sink's drain tailpiece above and the wall drain stub below. When it leaks, water pools in your cabinet. When it clogs, water backs up into your sink. Replacement means draining what little water sits in the trap, loosening two nuts, lifting out the old assembly, and threading in a new one with those same nuts. This is genuine entry-level plumbing work.

1. Stop the water, clear the space. Close the shutoff valves under the sink, or turn off the main water supply if you can't locate them. Open the cabinet door and empty everything underneath—cleaner bottles, sponges, the works. Place a bucket or shallow pan directly under the P-trap where it will catch water.
2. Loosen the top connection. Look at where the drain pipe from the sink enters the top of the P-trap. You'll see a large nut (usually 1.25 or 1.5 inches) holding it in place. Place your wrench on this nut and turn counterclockwise. It should spin freely by hand or with light wrench pressure—don't force it. Once loose, unscrew it the rest of the way by hand and set it aside.
3. Release the bottom connection. The bottom of the P-trap connects to a drain stub coming from the wall using another large compression nut. Grip this nut with your wrench and turn counterclockwise. Again, these nuts are hand-tight and shouldn't require force. Once loose, finish unscrewing by hand.
4. Lift out the old trap. With both nuts loose, the entire P-trap assembly should lift straight out. Tip it carefully into your bucket to catch any remaining water. If it feels stuck, wiggle it gently—there's usually a small amount of debris or mineral buildup. Don't force it; patient wiggling works better than strength.
5. Wipe the threads clean. Before installing the new trap, wipe the threaded male fittings (the parts that screw into the nuts) with a dry cloth or rag. Remove any debris, mineral deposits, or old pipe dope. These cleaned threads ensure a tight seal when you reassemble. Check that the rubber washer inside each nut is still intact—if it's cracked or missing, replace it.
6. Connect the top inlet. Position the new trap so its upper inlet aligns with the sink's drain tailpiece. Slide the compression nut onto the male fitting from the sink and hand-tighten it onto the tailpiece threads. Tighten it snug with your wrench—you want it tight enough to not leak but not so tight you strip the plastic threads. Stop when you feel definite resistance.
7. Secure the bottom outlet. Bend or position the trap so its lower outlet aligns with the wall drain stub. Slide the compression nut from that connection onto the outlet fitting. Hand-tighten it, then use your wrench to snug it down with the same firm but not crushing pressure you used at the top. Double-check that both nuts are equally tight.
8. Run water, check for leaks. Turn the water back on at the shutoff valves or main supply. Fill the sink completely and let it drain while you watch under the cabinet. Check both compression nuts for drips. A small bead of water at either nut means it needs another quarter-turn tighter. If water actively streams out, turn the water off and tighten more firmly.