Short answer
If only one sink is slow, the problem is in that sink. Check the stopper first: it may be set too low, or wrapped in hair. Then clean the P-trap and flush the overflow. If several drains are slow or gurgle together, the cause is further down the line or in the vent, and that is a job for a licensed plumber.
First, how many drains are slow?
This one question saves the most time. Run water in the slow sink, then in a nearby sink, the tub and the shower, and flush a toilet.
| What you see | Where the problem likely is | What to do |
|---|---|---|
| One sink slow, others fine | That sink: stopper, trap or overflow | Work through the steps below |
| Both bowls of a double sink slow | The shared trap or the trap arm | Clean the trap, then snake the trap arm |
| Several fixtures slow, or water rises in a tub when the sink drains | The branch or main drain line | Call a licensed plumber |
| Gurgling, a trap that keeps drying out, or sewer smell with slow draining | Venting | Call a licensed plumber |
The usual causes of one slow sink
A stopper set too low. On a lift rod pop-up, the stopper only rises as far as the linkage lets it. If the pivot rod sits in the wrong hole on the clevis strap, the stopper barely clears the drain and water has to squeeze around it. No clog, just a bad adjustment.
Hair at the stopper. In a bathroom sink this is the most common cause. Ask the Builder and HomeServe both start with pulling the stopper, and so should you.
Buildup in the trap. Soap scum, toothpaste and, in a kitchen, grease narrow the trap over months. The sink still drains, just slower each week.
A clogged overflow. The overflow channel lets air into the drain as water runs out. When the channel is packed with slime, the drain can glug and slow. It also smells; see why a sink drain smells.
A vent problem. Drains need air from the vent pipe to flow freely. A blocked or missing vent makes drains slow, gurgle and pull water out of traps. That is not a DIY repair for most people.
How to fix a slow sink drain, in order
What you need
Check how far the stopper opens
Push the lift rod all the way down so the stopper is open, and look at the gap. If it barely lifts off the drain, go under the sink, squeeze the spring clip, and move the pivot rod to a higher or lower hole on the clevis strap until the stopper rises well clear. Run water to test.
Pull and clean the stopper
Lift or twist the stopper out. If it is hooked to the pivot rod, loosen the pivot nut under the sink and pull the rod back so the stopper comes free. Clean off the hair and slime, then refit it. How to remove a sink stopper shows each type.
Clear the top of the drain
With the stopper out, run a plastic barbed strip down the drain and pull it up slowly. Repeat until it comes up clean.
Flush the overflow
Scrub inside the overflow opening with a small bottle brush, then pour a pitcher of hot tap water slowly into it. If it backs up out of the hole, the channel is packed and needs more brushing.
Plunge with the overflow sealed
Put an inch or two of water in the bowl, press a wet rag over the overflow, and plunge with short, sharp strokes, as The Home Depot describes. In a double kitchen sink, block the other drain instead.
Clean the P-trap
Set a bucket under the trap, unscrew both slip nuts, and empty and scrub the trap. Check the slip washers, refit it, and run water.
Snake the trap arm
If the trap was clean and the sink is still slow, feed a hand snake into the pipe going into the wall, work it through, and pull it back slowly. Refit the trap and check for leaks.
When it is the vent or the main line
If the steps above did nothing, or other fixtures are slow too, stop. Signs that the problem is beyond the sink:
- Several drains slow down at the same time.
- Gurgling from a sink or toilet when another fixture drains.
- Water backing up into a tub or shower when you run the sink or washer.
- A sewer smell that a clean trap and overflow do not fix.
A licensed plumber can run a camera down the line, clear it with a machine, and check the vent. Plunging one sink against a main line clog can push dirty water out of another drain.
Keep it flowing
- Use a hair catcher in bathroom sinks and a mesh basket in kitchen sinks. See the sink drain strainer guide.
- Pull and rinse a bathroom stopper every few weeks.
- Wipe greasy pans before washing them.
- Run hot tap water after use. A baking soda and vinegar routine is fine as mild upkeep, but it will not clear a real clog.
For a sink that has stopped draining entirely, go to how to unclog a bathroom sink or how to unclog a kitchen sink.
Questions people ask
Why does my bathroom sink drain slowly?
Most often hair and soap on the pop-up stopper, or a stopper that does not lift high enough when open. Pull the stopper and clean it, then check how far it rises. If both look fine, clean the P-trap.
Why does my sink drain slowly but is not clogged?
A stopper set too low can choke the flow even with no clog at all. Buildup that narrows the trap, a blocked overflow that lets air lock the drain, or a vent problem can also slow a sink without stopping it.
What does it mean if my sink gurgles when it drains?
Gurgling usually means air is being pulled through the trap because the drain cannot get air from the vent, or because of a partial blockage further down. If it happens at more than one fixture, call a plumber to check the vent and the main line.
Why are all my drains slow at once?
When sinks, tubs and toilets slow down together, the problem is usually in the main drain line or the vent stack, not in any one fixture. Plunging one sink will not fix it. A licensed plumber can scope and clear the line.
How do I adjust a pop-up stopper that does not open far enough?
Under the sink, squeeze the spring clip and slide the pivot rod into a different hole on the clevis strap, or loosen the clevis screw and move the strap on the lift rod. Test until the stopper lifts well clear of the drain when the rod is down.
Sources
Last reviewed October 12, 2026. Parts, sizes and listings change; check the product details before you buy, and follow the maker’s instructions.