How to clean a sink drain: stopper, overflow and P-trap

Step by step: how to clean a sink drain

Safety first. Do not use a chemical drain cleaner and then plunge or open the trap: it can splash and burn. Never mix drain cleaners with bleach, vinegar or each other, and wear gloves for the slime.

1. 1

   Remove the stopper

   Many bathroom pop-up stoppers lift straight out or come out with a quarter turn. If yours will not budge, look under the sink: a horizontal pivot rod enters the back of the drain pipe, held by a nut. Unscrew that nut by hand, pull the rod back an inch, lift the stopper out, and keep the parts in order.

2. 2

   Scrub the stopper clean

   Pull the hair off the stopper with a gloved hand and scrub the gray slime off with an old toothbrush and hot soapy water. That slime, a mix of soap, toothpaste and hair, is often the whole cause of a slow bathroom sink. Rinse it and set it aside.

3. 3

   Fish out the hair with a barbed tool

   Push a plastic barbed drain tool down the open drain, twist it a few times, and pull it straight up. Wipe off what it brings up and repeat until it comes out clean. In a kitchen sink, skip this and focus on grease and food in the strainer and trap.

4. 4

   Scrub the drain and overflow hole

   Run a narrow bottle brush down the drain opening as far as it reaches and through the overflow hole near the top of the basin. The overflow channel collects mildew and smells. Rinse with hot water as you go.

5. 5

   Flush with baking soda and vinegar

   Pour 1/2 cup of baking soda down the drain, then 1 cup of white vinegar, and let it fizz for 10 to 15 minutes. Flush slowly with a kettle of hot water. Use hot tap water rather than boiling water on plastic pipes or a porcelain basin.

6. 6

   Plunge if it still drains slowly

   Stuff a wet rag into the overflow hole, run 2 to 3 inches of water into the basin, and seal a flat-bottomed cup plunger over the drain. Plunge with short, quick strokes for 15 to 20 seconds, then lift and check. For a double kitchen sink, block the other drain first.

7. 7

   Rinse the P-trap for stubborn smells or clogs

   Put a bucket and a towel under the U-shaped pipe, unscrew the two slip nuts by hand (or gently with pliers), and empty the trap into the bucket. Rinse out the sludge, check the washers, and screw it back hand-tight. Run water for a minute and check for drips.

8. 8

   Put the stopper back and test

   Drop the stopper in, reconnect the pivot rod if you removed it, and tighten its nut by hand. Fill the sink, then open the stopper: the basin should empty in a few seconds with a steady swirl. A gurgle or slow drain means the clog is further down.

Why does my sink drain smell?

A smelly sink drain is almost always slime in the stopper, overflow or P-trap. Less often, a dry or damaged trap is letting sewer gas through.

Roto-Rooter’s guide to sink odors lists food and grease, bacteria and mold, a dirty or dry P-trap, and sewer gas leaks as the usual causes. It recommends cleaning the trap over a bucket and suggests enzyme drain cleaners for odor because they break down organic matter without harming pipes. A rotten egg smell that comes back after cleaning, or a sink that keeps clogging, is a reason to call a plumber.

A sink you rarely use, like a guest bathroom, can smell simply because the water in the trap evaporated. Run the tap for 30 seconds every week or two to refill it.

Bathroom sink drain vs kitchen sink drain

Bathroom drains clog with hair, soap and toothpaste; kitchen drains clog with grease and food. The cleaning order is the same, but the target is different.

Roto-Rooter’s plunging guide recommends a flat-bottomed cup plunger for sinks, not a flanged toilet plunger, and a snake or auger if plunging does not work. Their clog prevention tips include scraping grease into the trash and using a fine-mesh strainer. If you have a disposal, see our guide on how to clean a garbage disposal.

Should you use a chemical drain cleaner on a sink?

Use one only after a plunger and a barbed tool or snake have failed, and never on a sink that is completely blocked with standing water you will have to bail out.

Even professionals treat strong drain chemicals as a last resort. A Western Washington University facilities policy requires plungers and augers first, notes that drain cleaner seldom works on a fully stopped drain, and warns that mixing types of drain cleaner can cause a violent reaction and severe burns. At home, an enzyme cleaner for odors and mechanical tools for clogs cover nearly every situation.

Mistakes to avoid

• Pouring chemical drain cleaner into a sink full of standing water and then having to bail it out.
• Using a flanged toilet plunger on a flat sink, where it cannot seal.
• Forgetting to plug the overflow hole, so the plunger just pushes air out of it.
• Overtightening the plastic P-trap nuts with pliers and cracking them.
• Pouring grease or coffee grounds down the kitchen drain and flushing with hot water.