Bathroom sink draining slowly? Pop-up stoppers, P-traps and the overflow.

Bathroom sinks clog differently from kitchen sinks. There's no grease or food, just hair, soap scum and toothpaste, and they build up slowly in three or four predictable places: the pop-up stopper, the P-trap under the sink, the overflow channel and the short drain line in the wall. Work through them in that order.

First: is it only this sink?

Run water in the tub, the shower and the other sinks. If only the bathroom sink is slow, the problem is in the sink, its trap or its own drain line, and you can usually find it. If the tub and the sink in the same bathroom are both slow, they may share a branch line that's partly blocked. If several drains around the house are slow, a toilet gurgles when the sink drains, or water comes up in the tub, the problem is in the branch or main line. Stop using water and see what to do when the main line backs up. Our guide to why a drain keeps clogging covers those patterns.

1. The pop-up stopper

The stopper is where most slow bathroom sinks start. Hair wraps around the stopper's stem and the pivot rod that lifts it, then soap and toothpaste glue it into a mat that sits right in the drain opening. You often can't see it from above.

• Lift-out and click stoppers often pull straight out or unscrew from the top. Turn the cap counterclockwise and lift.
• Lever-operated stoppers are held by a pivot rod that enters the back of the drain pipe under the sink. Loosen the small nut, slide the rod out, and the stopper lifts free. Our guide on how to unclog a drain without chemicals walks through it.
• Check the lift. Sometimes the sink isn't clogged at all: the stopper only rises partway because the lift rod or its clip has slipped. Adjust the clip so the stopper opens fully.

Wipe the stopper clean, then run a plastic drain-cleaning strip (a barbed "zip" strip from any hardware store) down the drain to pull out the hair below it. That fixes a lot of slow sinks in five minutes.

2. The P-trap under the sink

The U-shaped bend under the sink holds a little water to keep sewer gas out of the bathroom. It also collects whatever gets past the stopper: toothpaste, soap, hair, hair product, and the occasional earring back or bottle cap.

To clean it, put a bucket and a towel under the trap, loosen the two slip nuts by hand (plastic traps) and drop the trap out. Rinse it, look into the pipe going into the wall, and reassemble it with the washers facing the way they came off. Run water and check for drips. In older Burbank and Glendale homes, chrome or brass traps can be corroded thin. If a nut won't turn or the pipe flexes, stop before it snaps. A replacement trap is a small job, but a broken one under a full sink isn't fun.

3. The overflow

Most bathroom sinks have an overflow hole near the rim. It leads to a channel in the porcelain that joins the drain below the stopper. It keeps the basin from overflowing, and it also lets air in behind the water as the sink empties. When that channel fills with soap scum and mildew, it can smell musty or like sewage, and the sink may drain a little slower. Clean it with a small bottle brush and hot water. A gunked overflow rarely causes a full clog by itself, so if the sink is very slow, the stopper or trap is still the likely cause. If the smell is coming from somewhere else, see sewer smell in the house.

4. Past the trap: the line in the wall

If the stopper and trap are clean and the sink is still slow, the buildup is in the drain arm that runs from the trap into the wall and down to the branch line. In older Valley homes that pipe may be galvanized steel, which narrows with scale and soap over decades. A small handheld drain auger fed through the trap opening can clear it; see how to use a drain snake. Gurgling when the sink drains, or a sink that slows down again within weeks, can point to a vent problem or a partial blockage farther down. Our gurgling drains guide explains the difference. At that point a professional drain cleaning is the right call.

What it costs to clear a bathroom sink in LA

These are published ranges from LA-area plumbers and cost guides. They're a sanity check, not a quote.

At Rooter Pros, sink, tub and toilet drains get a free estimate: call (818) 669-9019 and you get the price before any work begins. New customers can also ask about our $49 first-time drain cleaning coupon: new customers only, one per household, one drain or line per visit, residential only, Monday–Friday 7am–5pm, accessible ground-level cleanout required, not valid with other offers. It's a new-customer special, not our regular rate. If the drains keep coming back, call us for a free estimate on a sewer camera inspection. See our pricing page and the drain cleaning cost guide for more.

How to keep it from coming back

1. Use a hair catcher or a stopper with a strainer, especially if anyone shaves, trims or brushes long hair over the sink.
2. Pull and wipe the stopper every month or two. It takes a minute and prevents most clogs.
3. Run hot water for a few seconds after toothpaste, shaving cream or thick soap.
4. Brush out the overflow when you clean the sink.
5. Skip chemical drain openers. They don't dissolve hair well and they're hard on old metal traps.
6. Watch the pattern. If the sink and the tub slow down together, the shared line needs attention. See also why a bathtub drain keeps clogging.

When to call

Call a plumber if more than one drain is slow, water backs up into the tub or another sink, the sink slows again within weeks of cleaning, the trap or its nuts are corroded, you smell sewage, or the stopper, trap and a hand auger don't clear it. If you've used a chemical opener, say so before anyone opens the trap.

Related: Drain cleaning · Drain clogged after a remodel · Unclog a drain without chemicals · How to use a drain snake · Why a drain keeps clogging · Gurgling drains · Sewer smell in the house · Bathtub drain keeps clogging · Kitchen sink keeps clogging · Toilet keeps clogging · Drain cleaning cost · All plumbing tips · Serving Burbank, Glendale, Los Angeles & Santa Clarita

Prices in the table are typical published ranges from other Los Angeles-area plumbers and cost guides as of October 2026. They are not Rooter Pros quotes and change over time. Your price depends on your home. Sources are linked in the table.