How to Unclog a Kitchen Sink
Kitchen sink clogs are almost always caused by grease. Even if you never pour cooking oil down the drain, grease from dishes, sauces, and food scraps coats the inside of your pipes with every wash. Over weeks and months, that coating thickens until water barely trickles through. The good news: most kitchen clogs respond to a simple escalation of methods — start with boiling water, move to baking soda and vinegar, try plunging, and if all else fails, clean the P-trap. You'll clear most clogs in under 30 minutes.
Time Required
15-45 minutes
Difficulty
Easy to Moderate
When to Call a Pro
If clog is past the wall
Method 1: Boiling Water
Remove standing water from the sink
If the sink is full of backed-up water, bail it out into a bucket first. The boiling water needs to contact the clog directly, not mix with a pool of cold water sitting above it.
Boil a full kettle of water
You want at least a half-gallon of boiling water. A full tea kettle or large pot works. If your drain pipes are PVC (white plastic), use very hot tap water instead — a rolling boil can soften PVC joints over time.
Pour in stages directly into the drain
Pour about a third of the water directly into the drain opening. Wait 5-10 seconds for the heat to work on the grease, then pour another third. Repeat with the last portion. If the water drains through, you've likely cleared it. If it sits, move to Method 2.
Method 2: Baking Soda and Vinegar
- Pour 1/2 cup baking soda into the drain: Push it down into the opening with a spoon if needed. The baking soda needs to reach the clog, not just sit on the drain grate.
- Add 1/2 cup white vinegar: The fizzing reaction helps break up grease and food particles. Immediately cover the drain with a wet cloth or plug to force the reaction downward through the pipe.
- Wait 15-30 minutes: Give the mixture time to dissolve the grease buildup. For stubborn clogs, you can wait up to an hour.
- Flush with boiling water: Pour a full kettle of boiling water down the drain to flush the loosened material through. You can repeat this entire process 2-3 times for tough clogs.
- For double sinks: Treat both drains, as they connect to the same P-trap and branch line. A clog in one side usually affects both.
Method 3: Plunging the Sink
Fill the sink with 3-4 inches of water
You need water in the sink for the plunger to create proper suction. The water transmits the pressure from the plunger into the drain pipe.
Block the other drain and overflow
If you have a double sink, stuff a wet rag tightly into the second drain opening. This prevents the plunger pressure from escaping through the other side. Also block the dishwasher air gap if visible on the countertop.
Plunge vigorously 15-20 times
Use a flat-bottomed cup plunger (not the flanged type for toilets). Place it over the drain, push down to create a seal, and pump rapidly 15-20 times. Pull up sharply on the last stroke to create suction. Repeat 3-4 sets if the first round doesn't work.
Method 4: Clean the P-Trap
- Place a bucket under the P-trap: The P-trap is the curved pipe section under the sink. It holds water and will spill when removed, along with whatever caused the clog.
- Unscrew the slip nuts: Most P-traps have hand-tightened slip nuts at both ends. Turn them counterclockwise to loosen. If they're too tight, use slip-joint pliers with a cloth to protect the finish. Plastic P-traps are especially easy to remove by hand.
- Remove and clean the trap: Pull the curved section free and dump the contents into the bucket. You'll likely find a thick sludge of grease, food particles, and grime. Scrub the inside of the trap with a bottle brush and dish soap. Rinse it out in another sink or with a hose.
- Inspect the pipe going into the wall: While the trap is off, shine a flashlight into the pipe stub going into the wall. If you can see buildup in there, use a drain snake to clear it before reassembling.
- Reassemble and check for leaks: Hand-tighten the slip nuts, run water for 30 seconds, and check both connections for drips. A quarter turn with pliers is usually enough if hand-tight isn't sealing.
Grease Prevention Habits
- Wipe greasy pans with paper towels first: Before washing any pan with cooking oil, butter, or grease, wipe it down with a paper towel and throw it in the trash. This removes 90% of the grease before it enters your drain.
- Collect cooking oil in a container: Keep an old jar or can next to the stove. Pour used cooking oil into it instead of down the drain. When full, throw it in the trash or take it to a recycling center.
- Run hot water after washing dishes: After doing dishes, run the hot tap for 30 seconds. This helps flush any residual grease through the drain line before it solidifies and sticks to the pipe walls.
- Monthly baking soda flush: Once a month, do a preventive baking soda and vinegar flush followed by boiling water. This dissolves grease buildup before it becomes a clog.
Pro Tips
- •Dish soap and hot water for grease: Squirt a tablespoon of dish soap (Dawn or similar) directly into the drain, then follow with boiling water. The soap emulsifies grease and helps it flush through rather than re-sticking downstream.
- •Salt boosts the reaction: Add 1/2 cup of table salt along with the baking soda before pouring vinegar. The salt acts as a mild abrasive against the pipe walls and improves the cleaning action.
- •Don't forget the dishwasher connection: If your kitchen sink clogs and water backs up into the dishwasher (or vice versa), the clog is in the shared drain line after the disposal. The P-trap method will usually find it.
- •Check the garbage disposal first: Before trying any unclogging method, run the disposal with cold water. A disposal jammed with food can back up the whole sink. Press the reset button on the bottom of the unit if it won't turn on.
Frequently Asked Questions
Can I pour boiling water down a kitchen sink with a garbage disposal?
Yes, boiling water is safe for garbage disposals and the connecting pipes. It helps melt grease that coats the disposal chamber and drain line. However, if your drain pipes are PVC (white plastic), use very hot tap water instead of a full boil, as repeated boiling water can soften PVC pipe joints over time.
Why does my kitchen sink clog but the garbage disposal works fine?
The disposal grinds food but doesn't prevent grease buildup downstream. Grease coats the inside of the drainpipe past the disposal, gradually narrowing the opening until water can't flow through. The clog is typically in the P-trap or the horizontal pipe running to the wall. Running cold water during and after using the disposal helps solidify grease so it gets flushed rather than coating pipes.
Is it safe to plunge a kitchen sink with a garbage disposal?
Yes, plunging a sink with a disposal is safe as long as the disposal is turned off. Make sure the power switch is off before plunging. The plunger creates pressure in the drain line past the disposal, which can dislodge clogs in the P-trap or branch drain. Never put your hand in the disposal to check for clogs while it's connected to power.