A kitchen sink draining slowly almost always has grease, food scraps and soap residue built up in the trap under the sink or in the first stretch of pipe behind it. Clear it mechanically, in this order: the strainer and disposal, a cup plunger with the other openings sealed, the P-trap by hand over a bucket, then a hand auger. Skip caustic drain cleaners. They are corrosive, they burn skin on contact, and if they fail you are left working on a pipe full of them.
If more than one drain in the house is slow, stop here. That is not a kitchen clog.
First: is it only the kitchen sink?
Fill the sink a few inches and let it go. Then run the bathroom sink and the tub, and flush a toilet.
- Only the kitchen sink is slow. The clog is in the kitchen branch: the trap, the trap arm, or the pipe inside the wall behind it. Most of this article applies.
- Several drains are slow, or water gurgles up in one fixture when another drains. The blockage is further down, in the main drain or the sewer line, or the venting is involved. That is a licensed plumber's job, and plunging a kitchen sink will not reach it.
- The sink smells of sewage as well as draining slowly. Read what a sewage smell at the kitchen sink actually means first. A smell and a slow drain together can point to venting, which is behind the wall.
Why kitchen sinks slow down
Kitchen drains fail differently from bathroom drains. The bathroom clog is hair. The kitchen clog is fat.
Cooking grease goes down warm and liquid, then cools in the pipe. It coats the inside of the trap and the pipe walls, and everything else sticks to it: rice, pasta, coffee grounds, eggshell grit, bits of peel. Soap residue binds it together. The result is a soft, narrowing sleeve that slows the drain for weeks before it stops it.
That is why the fix is mechanical. The blockage is a physical plug sitting in a pipe you can mostly reach.
If you have already poured a chemical cleaner in
This is the section most guides leave out, and it matters most if it applies to you.
If a drain cleaner is sitting in a sink that has not drained, do not plunge it, do not open the trap, and do not pour in a second product. Plunging splashes it back up at you. Opening the trap drops it on your hands and into the cabinet.
Poison Control's guidance on caustic household products, read on 2026-09-11, is direct about why: chemical burns occur instantly if these products touch your mouth, eyes, or skin. Its article on what is in drain cleaner, read the same day, lists the usual acid ingredients as sulfuric and hydrochloric acids and the usual alkaline ones as sodium and potassium hydroxide.
Read the product's label for what to do next. If the water will not drain, tell the plumber exactly what you used, and when, before they start. If any gets on skin or in eyes, Poison Control's advice is to rinse immediately with running water, for at least 20 minutes for eyes, and to call 1-800-222-1222 or use webPOISONCONTROL online.
Step 1: the strainer and the disposal
Pull out the strainer basket and clean it. Then, if you have a garbage disposal, treat it as part of the drain, because it is.
A disposal that hums without turning, or grinds slowly, can back up the sink it sits under. Turn it off at the switch and, if it plugs in under the sink, unplug it before anything goes near the opening. Never put a hand into a disposal. Many models have a reset button on the underside and a socket for a hex key that turns the motor by hand from below; your disposal's manual covers both for your model. If it smells as well, a disposal that has started to smell walks through cleaning it properly.
In a double sink with a disposal on one side, run the disposal before you blame the drain. The two bowls often share one trap.
Step 2: plunge it properly
A plunger works on a kitchen sink, but only when the pressure has nowhere else to escape.
- Use a flat cup plunger, not the flanged kind made for toilets. The flat rim seals on a flat sink bottom.
- Seal the other openings. In a double sink, plug the second drain with a stopper or a wet cloth held down firmly. Cover the overflow hole too if the sink has one.
- Mind the dishwasher. If your dishwasher drains into this sink or disposal, plunging can push dirty water back up its hose, and an air gap on the sink deck may spit water. Keep a towel over the air gap. If the dishwasher has stopped draining too, the guide to a dishwasher that isn't draining explains how to tell a shared-drain problem from a machine problem.
- Leave a few inches of water in the sink so the plunger pushes water, not air.
- Plunge in firm, straight strokes, then pull the plunger off and watch whether the water drops.
If the water goes down and stays down, run hot tap water for a minute to carry the loosened grease past the trap. If nothing moves after a few rounds, go to the trap.
Step 3: clean the P-trap by hand
The P-trap is the curved section of pipe directly under the sink. It holds water to block sewer gas, and it is where most kitchen clogs sit.
- Clear the cabinet and put a bucket and old towels directly under the trap.
- Put on rubber gloves and eye protection. The water in the trap is dirty, and worse if any cleaner has been poured in.
- On most plastic traps, the two large slip nuts loosen by hand. Unscrew them, keep the trap level until it is over the bucket, then tip it out.
- Clear the trap with a bottle brush, and shine a flashlight into the pipe that runs back into the wall, the trap arm.
- Check the washers inside the slip nuts and refit them the same way round.
- Reassemble hand-tight, run water, and check every joint for drips with a dry paper towel.
Stop conditions. If the trap is metal and badly corroded, if the joints are glued rather than threaded, if a slip nut will not loosen by hand without heavy force, or if the trap arm moves or crumbles where it enters the wall, stop and book a licensed plumber. An old trap can break when disturbed, and then the sink is out of service until it is replaced.
Step 4: a hand auger for the trap arm
If the trap was clean, the clog is further in. With the trap off, a hand-crank drain auger, often called a drain snake, can be fed into the trap arm and a short way down the line.
Feed the cable in slowly, turning the handle as you go. When it meets resistance, keep turning and push gently. The aim is to bore through or hook the plug, not to force the cable. Pull it back, wipe it into the bucket, and repeat until it runs freely.
Two limits apply. Hand augers only: powered drum machines can whip and kink the cable, and they belong with plumbers trained on them. And if the auger will not pass, or the clog is beyond what a hand auger reaches, the problem is in the drain line inside the wall or below the floor. That is a licensed plumber's job.
What about baking soda and vinegar?
Honest answer: baking soda and vinegar fizz impressively, and the fizz is mostly the two reacting with each other. It will not dissolve a plug of grease and food. On a drain that is merely sluggish it does no harm, followed by hot tap water, but it is not a clog fix. Enzyme drain products are generally sold for maintenance and work slowly by design; follow the label.
The rule that holds for all of them: never combine cleaning products in a drain, because mixing can release toxic gas. The EPA's brief guide to mold, moisture and your home, updated February 2026 and read on 2026-09-11, warns never to mix chlorine bleach solution with cleaning products that contain ammonia, because toxic fumes could be produced. A drain holding an unknown mix of earlier products is exactly where that happens by accident.
Why we skip caustic drain cleaners altogether
- They burn. Poison Control lists drain cleaner among caustic household products that burn on contact.
- They are corrosive. The property that burns skin is the same one that attacks materials, and an old metal trap or drain line already thinned by age is the part least able to take it.
- They often fail on the clogs kitchens actually get. A dense plug of fat and food is a physical object. When the product does not clear it, the sink holds a corrosive liquid, and every mechanical step afterward becomes more dangerous, for you or for the plumber.
Keep it from coming back
- Grease goes in the trash, not the drain. Let it cool in a can or jar, then bin it.
- Scrape plates into the trash before rinsing, disposal or not.
- Keep the strainer basket in whenever the disposal is not running.
- Make the drain part of the routine. A strainer clean and a hot-water flush belong in a realistic kitchen cleaning schedule for exactly this reason.
When the kitchen sink draining slowly is a plumber's problem
- More than one drain is slow, or fixtures gurgle when another one drains.
- Water backs up into the other bowl, the dishwasher, or another room.
- The sink smells of sewage and refilling the trap does not fix it.
- The clog comes back within weeks of clearing it.
- The trap or trap arm is corroded, glued, or will not come apart by hand.
- A chemical cleaner is sitting in a sink that will not drain.
FAQ
Why is my kitchen sink draining slowly but not fully clogged? Grease and food build up gradually on the inside of the trap and drain pipe, narrowing it a little at a time. The sink slows for weeks before it stops, which makes a slow drain the best time to clean the trap.
Is it safe to plunge a kitchen sink with a garbage disposal? Yes, with the disposal switched off (and unplugged, if it plugs in), the second bowl sealed, and a towel over the dishwasher air gap if you have one. Never plunge a sink with a chemical cleaner sitting in it.
Does boiling water unclog a kitchen sink? Hot water can soften fresh grease, but pouring a kettle of boiling water into a sink that is already holding water is a splash and scald risk, and it does nothing for a clog made of food. Very hot tap water after plunging does the useful part more safely.
The short version
Check that only the kitchen is slow. Clean the strainer and disposal, plunge with every other opening sealed, open the trap over a bucket, then use a hand auger. If the clog is past the trap arm, or more than one drain is involved, it is a plumber's call, and a chemical would only have made that call more dangerous.
