What to Do When Sink Won't Drain: A Troubleshooting Guide

What typically causes a sink to stop draining

A sink that won’t drain is usually the result of buildup inside the drain path. In kitchens, grease, soap scum, and food particles accumulate in the trap and pipes; in bathrooms, hair is the main culprit. Over time these deposits form a partial obstruction that slows or stops flow. A vent blockage or a poorly pitched drain can also contribute, especially in multi-story homes. If you’re asking what to do when sink won’t drain, start with the simplest checks and move toward physical cleaning. Addressing the root cause quickly saves water, reduces mess, and minimizes the chance of a full clog. Drain Guide emphasizes methodical, safe steps over guesswork.

Quick checks you can do before disassembly

Before taking apart the plumbing, try these fast checks that solve many cases:

• Inspect the pop-up stopper or bathroom grid; ensure it isn’t misaligned or seized.
• Remove visible debris from the stopper and the drain opening.
• Rinse with hot water to melt grease and flush minor accumulations.
• If you have a double kitchen sink, check the adjacent side’s flow as a clue to whether the blockage is downstream.
• Try a plunger designed for sinks; ensure a tight seal and use several firm, controlled pushes.

If the sink still won’t drain after these steps, you’re ready to move to more involved cleaning. Safety: wear gloves and eye protection when dealing with dirty water.

Step 1: Inspect and clean the P-trap

The P-trap is the U-shaped pipe under the sink and is a common clog point. Place a bucket underneath, loosen the slip nuts with adjustable pliers, and slowly remove the trap. Clear out hair, food scraps, and gunk with a brush, then rinse the trap with hot water. Reassemble and run water to check for leaks.

Tip: take a photo of how the trap fits before disassembly so you can reassemble accurately.

Step 2: Clear the stopper assembly

Pop-up stoppers in kitchen or bathroom sinks can trap debris. Remove the linkage, pull out the stopper, and clean any hair or gunk from the seal and threads. Reinstall snugly but not overtight. After reassembly, run hot water to see if flow improves.

Tip: keep small tools away from your eyes; use a flashlight to inspect hard-to-reach areas.

Step 3: Plunge smartly

A plunger can break up minor clogs without chemicals. Fill the sink with a small amount of water to cover the plunger base, seal well, and push with steady pressure for 20–30 seconds. If you have a double sink, block the other drain with a plug to maintain suction. Repeat a few times.

Tip: if the water won’t rise, add a bit more water to improve suction before plunging.

Step 4: Snaking the drain

A drain snake (plumbing auger) reaches past minor blockages in the pipes. Insert the stiff end into the drain and rotate while pushing forward. When you feel resistance, back off and pull out debris. Rinse with hot water as you retract to clear fragments.

Tip: wear gloves; never force the snake into a hard obstruction—rotate and back out gently.

Step 5: Garbage disposal and vent considerations

If you have a garbage disposal, run it with cold water to check for grinding noise and jams. Do not put fibrous or starchy materials down the disposal. A blocked vent can also cause slow drainage; if you hear gurgling in the drains, a vent line might be blocked and may require professional attention.

Tip: avoid chemical cleaners near disposals because fumes can be hazardous.

Step 6: Chemical cleaners and when to avoid them

Chemical drain cleaners can be tempting, but they pose risks to skin, eyes, and septic systems. Never mix cleaners, and avoid caustic formulas in PVC pipes. If your sink still won’t drain after mechanical clearing, or you suspect a vent or sewer issue, it’s time to call a licensed plumber. Urgent situations like multiple fixtures backing up may require immediate service, especially in homes with septic systems.

Tip: use mechanical methods first; reserve chemicals as a last resort and always follow label directions.

Step 7: Final test and cleanup

After clearing, reassemble all components, run hot water for several minutes, and monitor for any leaks. Check the other fixtures in the house to ensure there’s no shared venting issue. Keep notes about what worked for future reference and prevention.

Step 8: When to call a professional

If the clog persists after a thorough mechanical approach, or you notice repeated backups, it’s wise to call a licensed plumber. Persistent slow draining can indicate deeper issues like sewer line problems, vent stack failures, or mis-pitched pipes that require specialized equipment.