Bathroom sinks: hair and soap
The pop-up stopper collects hair, and soap binds it into a plug. Pull the stopper out (on most sinks it lifts straight up or releases from a pivot rod behind the drain), clean it, and the sink often drains normally again.
Kitchen sinks: grease and food
Grease poured down a kitchen sink cools and coats the pipe, trapping food until the drain closes. If you have a garbage disposal, a jammed or clogged disposal can also stop the sink.
- Run the disposal and listen — humming means it's jammed
- Clean the P-trap under the sink with a bucket underneath
- Don't pour chemical drain cleaner into standing water in a sink with a disposal
Signs the clog is past the sink
A kitchen sink that backs up when the dishwasher drains, a bathroom sink that gurgles when the toilet flushes, or water rising in a nearby tub all mean the blockage is in a shared branch line or the main. That needs a drain machine, not a plunger.
When clogs keep coming back
A sink that clogs every few months has buildup a snake only punches through. Hydro jetting cleans the pipe wall, and a camera inspection shows whether there's a sag or break collecting debris.
Kitchen sink vs. bathroom sink: different clogs, different fixes
The fix depends on which sink it is. Kitchen clogs are usually grease that cooled and hardened in the drain, plus food scraps and coffee grounds; they build up gradually and often sit past the trap, in the wall or the branch line. Bathroom sink clogs are almost always hair and soap scum caught on the pop-up stopper, within a few inches of the drain opening.
- Bathroom sink: pull or unscrew the pop-up stopper and clean it; a plastic drain stick or the stopper's own linkage usually clears it
- Kitchen sink, one side slow: if you have a disposal, run it, check its reset button, and make sure the dishwasher drain connection isn't clogged
- Kitchen sink, both sides slow: the blockage is past the trap; a sink plunger with the other side plugged, then a hand auger through the trap arm
- Kitchen sink backs up when the dishwasher drains: blockage in the shared line past the trap
- Both kitchen and bathroom fixtures slow at once, or gurgling toilets: that's the main line, not the sink
When to call a plumber for a slow sink
Call when the sink backs up after you've cleaned the trap, when water comes up in the other side of a double kitchen sink, or when more than one fixture is slow. Those signs point to a blockage further down the line, which needs a cable or jetting.
Sink Not Draining? Causes and Fixes: when to call a pro
- Several drains are slow at once
- Water comes up in a different fixture
- You've used chemical cleaners — tell the plumber before they open the line
Sink Not Draining? Causes and Fixes: common questions
Can I use chemical drain cleaner in a slow sink?
It's better not to. Caustic cleaners can damage older pipes and fixtures and are dangerous if a plumber later has to open the line. A plunger, the trap, or a hand auger usually works better.
Why does my bathroom sink drain slowly?
Hair and soap buildup on the pop-up stopper is the most common cause. Removing and cleaning the stopper fixes most slow bathroom sinks.
Why is my kitchen sink not draining?
Grease and food solids in the trap or branch line are the usual cause. If both sides of a double sink are slow, the clog is past the trap.
Can I remove the P-trap myself?
Yes, with a bucket underneath. Loosen the slip nuts, clean the trap, and reassemble hand-tight.
Every home differs; editorial standards.