OnOtto
Menu

How do you clean a sink P-trap?

Updated August 2026

15–20 minutes · Easy DIY

← All how-to guides

Slide a bucket under the U-bend, back off the two slip nuts, and wash the trap out: 15 to 20 minutes, no chemicals. That curved section under the sink is where hair, soap scum, and kitchen grease collect first, which is why a slow bathroom sink that ignores a plunger clears the moment the bend comes off. Traps are 1-1/4 inch on a lavatory and 1-1/2 inch on a kitchen sink. The only parts you may need are the beveled washers, about $2 a pair.

What you need

Before you start: If anyone poured chemical drain cleaner into this sink in the last few days, that caustic liquid is still sitting in the trap. Wear rubber gloves and eye protection, open the nuts slowly, and keep your face out of the splash line. The trap water is also your sewer gas seal, so the drain will smell while it is open and the seal has to be refilled before you walk away: run the tap for a minute after reassembly. Bail out a standing sink first, or several gallons land in a one-gallon bucket.

Steps

  1. Empty the cabinet and lay towels down. Whatever comes out of that trap will find the one thing you did not move.
  2. Set the bucket directly under the bend. A kitchen trap holds close to a quart of water and releases all of it at once.
  3. Loosen the two slip nuts, one at the vertical tailpiece and one at the arm going into the wall. Plastic nuts usually spin off by hand; on chrome, wrap a rag around the nut before the pliers touch it.
  4. Slide both nuts back along the pipes and pull the bend free. Tip the contents into the bucket, not into the sink you are about to reassemble.
  5. Scrub the inside with an old toothbrush and hot soapy water. Then run the brush into the tailpiece above and into the trap arm, since the clog often sits an inch or two past the joint rather than in the bend itself.
  6. Inspect both beveled nylon washers. Flattened, cracked, or hardened washers are the usual reason a rebuilt trap weeps. A new pair is about $2, and the bevel always points into the joint.
  7. Reassemble by hand. Start each nut straight to avoid cross-threading, then snug it no more than a quarter turn past hand tight. Plastic slip nuts crack easily and a cracked nut leaks forever.
  8. Run hot water for a full minute with a dry paper towel wrapped around each joint. Any dampness on the towel means one more small turn, or a washer that is not seated square.

Or hire it out

A plumber charges $100 to $200 to pull and clean a trap, with the minimum service call driving most of that price. Snaking a deeper branch line runs $150 to $350.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for drain cleanings sets itself.

Log this task, get the next reminder

Frequently asked questions

The sink is still slow after I cleaned the trap. What next?

Test another fixture on the same wall. If the tub and the sink are both sluggish, the clog is downstream in the branch line, not in your trap, and a 15-foot hand snake fed into the trap arm is the next move. Gurgling from a nearby drain when this one runs points at a blocked vent instead, which is a roof job. Ignoring either one gets expensive; see the cost of ignoring slow drains.

Why does the sink still smell after the trap is clean?

Three common causes. Biofilm coats the drain walls and the overflow opening above the trap, so scrub those with a bottle brush and hot soapy water. A guest bathroom that goes unused dries its trap out and lets sewer gas straight in, which one quart of water a month prevents. A failed vent siphons the seal out during a big flush. The seal itself is the whole point of the fitting: what a P-trap is.

It leaks at the joint after reassembly. What did I do wrong?

Usually one of three things: the washer is upside down, the nut is cross-threaded, or the trap arm is not pushed far enough into the wall fitting. Take it apart and start over rather than tightening harder, because more torque on a plastic nut cracks it. Diagnostics by drip location are on why a P-trap leaks under the sink, and the schedule that keeps you out of there is how often to clean a sink P-trap.

Related