To unclog a double-basin kitchen sink without chemicals, work the fixes in order of what clears the most clogs fastest: pour boiling water and dish soap down the drain, then plunge the clogged side while you seal the other basin (and the garbage disposal opening) so you don’t lose pressure. If plunging fails, reset the disposal, then slide a bucket under the cabinet and remove the P-trap to clean out the grease and food packed inside. Skip the chemical drain cleaner entirely — it rarely clears a full grease clog, it can soften PVC and corrode metal, and it turns any later plunging or trap removal into a caustic-splash hazard. A hand auger down the trap arm handles the stubborn ones.
Likely causes, ranked
Double-basin sinks share one trap arm and drain line, so a clog on one side usually backs up both. Here’s what to check, most-likely first.
| Cause | How to tell | Fix |
|---|---|---|
| Grease & food buildup in the trap arm | Both basins drain slowly or hold water; gurgling. Most common by far. | Boiling water + soap, then plunge; remove and clean the P-trap and trap arm. |
| Garbage disposal side jam | Disposal hums but won’t spin, or won’t turn on at all. Water pools on the disposal side. | Reset the disposal; free the flywheel with the hex key. |
| Garbage disposal clog | Disposal runs fine but drains slowly; food slurry sits in the chamber. | Clear the chamber and the drain elbow below it. See our guide to a clogged garbage disposal. |
| Deeper branch-line clog | Sink clears briefly then backs up again; nearby fixtures gurgle when the sink drains. | Snake the trap arm with a 25-ft hand auger. |
How to unclog it, step by step
Go in this order and stop as soon as the water drains. Each step escalates only if the last one didn’t work. If you’ve already poured chemical drain cleaner in, do not plunge or open the trap — the standing water is now caustic and can splash your eyes and skin. Wait for a pro or flush with lots of cold water and full protective gear first.
- Boiling water and dish soap. Squirt a good shot of dish soap into the drain, then pour a kettle of near-boiling water down in stages. The soap emulsifies grease and the heat loosens it. This alone clears a surprising number of soft food-and-fat clogs. (Use hot-but-not-boiling water if you have PVC traps.)
- Plunge — and seal the OTHER basin. This is the step people get wrong on a double sink. A sink (cup) plunger only builds pressure if the system is sealed. On the non-disposal side: stuff a wet rag into the other basin’s drain, or press a flat stopper or a second plunger over it, and hold it down hard — otherwise your force just shoots up the open drain. Run an inch or two of water in the clogged basin to cover the plunger cup, seat the cup over the drain, and plunge straight up and down 10–15 times, breaking the seal sharply on the last pull. Repeat a couple of times.
- Plunging the disposal side. If the clog is on the disposal basin, you also have to seal the disposal itself — pressure escapes up through it. Have a helper hold a flat stopper or a wet rag firmly over the disposal opening (or clamp the dishwasher hose if one is connected) while you plunge the other drain, or plunge the disposal drain directly with the opposite basin sealed. No seal, no suction.
- Check and reset the disposal. If it hummed or stayed dead, cut the power at the wall switch. Press the small red reset button on the underside of the unit. Then fit the disposal hex key into the center socket on the bottom and rock it back and forth to free the flywheel. Fish out any visible debris from the top with tongs (never your hand), restore power, and run cold water while you test it.
- Remove and clean the P-trap. Still clogged? The grease plug is usually right here. Clear everything out of the cabinet and set a bucket directly under the U-shaped trap. Loosen the two slip nuts by hand, counter-clockwise — use channel-lock pliers to break them free if they’re tight — then pull the trap down and dump it into the bucket. Scrub out the grease and gunk with a bottle brush. While it’s apart, push a brush or straightened hanger into the trap arm (the horizontal pipe heading into the wall), since clogs love to sit there. Check the washers, reseat the trap, and hand-tighten the nuts plus about a quarter-turn with pliers — no more, or you’ll crack the plastic.
- Snake the trap arm. If the water still won’t move, the clog is past the trap in the branch line. With the trap off, feed a 25-ft hand auger (drum snake) into the trap arm, crank it until you feel the blockage, work through it, then pull the cable back cleaning it as you go. Reassemble the trap and flush with hot water to confirm it’s clear.
Tools & parts you’ll need
- Sink (cup) plunger — the flat-bottomed kind, not a flanged toilet plunger
- Bucket — for the trap water and debris
- Channel-lock pliers — to break loose stubborn slip nuts
- Hand auger / 25-ft drum snake — for the trap arm and branch line
- Garbage disposal hex key (¼-inch Allen wrench) — to free a jammed flywheel
- Replacement trap washers — cheap slip-joint washers in case the old ones are cracked
- Bottle brush or straightened coat hanger, rags, and rubber gloves
DIY cost vs. calling a pro
Almost every kitchen-sink clog is a DIY job. You’re mostly paying for tools you’ll keep. Pro prices below are typical US ranges for 2026.
| Approach | Cost | Notes |
|---|---|---|
| Plunger + dish soap (DIY) | $0–$15 | Clears most soft clogs; plunger is a one-time buy. |
| Hand auger / drum snake (DIY) | $15–$100 | Handheld or drill-driven, reaches ~25 ft for trap-arm clogs. |
| Plumber snakes the sink drain | $100–$225 (avg ~$175) | Trip/diagnostic fee may apply; often credited toward the work. |
| After-hours / emergency call | +$50–$150 surcharge | Nights, weekends, and holidays cost more. |
Difficulty & time
Easy to moderate; 15–60 minutes. Plunging takes minutes; pulling the P-trap adds a messy but simple half-hour with basic tools.
When to call a licensed plumber
- Multiple fixtures back up at once — if the tub, toilet, or floor drain gurgle or flood when you run the sink, the clog is in the main line, not your trap. That’s a pro job.
- The same clog keeps coming back within days or weeks, even after snaking — a sign of a partial break, a belly in the line, or grease deep in the branch.
- Sewage smell or dark water backing up, or you can’t reassemble the trap without leaks.
- You already poured chemical drain cleaner and the sink still won’t drain — tell the plumber so they can protect themselves.
FAQ
Why not just use a chemical drain cleaner?
Because it’s the worst option for a kitchen sink. Caustic cleaners generate heat that can soften PVC and corrode older metal pipes, they rarely dissolve a full grease-and-food plug, and the leftover residue sits in the trap. If you later have to plunge or open the P-trap — which you often do — you’re now working with caustic liquid that can burn skin and eyes. Physical methods (plunge, trap cleaning, snake) fix the actual clog without the hazard. This Old House makes the same case for mechanical clearing over chemicals.
How do I plunge one side of a double sink?
Seal the other basin completely first. Plunger pressure follows the path of least resistance, and on a double sink that shared drain lets your force escape straight up the open basin. Block the other drain with a wet rag, a flat stopper, or a second plunger held down hard, and if that side has a disposal, seal the disposal opening too. Then plunge the clogged side. Without the seal you’ll get almost no suction.
Does baking soda and vinegar actually work?
It’s mild — fine for freshening a slow drain or light odor, but the fizzing reaction is gentle and won’t punch through a solid grease clog. Use it for maintenance, not as your main unclogging tool. Boiling water with dish soap does more for grease, and a plunger or trap cleaning does the real work.
Water backs up into the other basin when I run the disposal — what’s that mean?
The clog is downstream of where both basins join, in the shared trap arm or branch line, so water from the disposal side has nowhere to go but up the other drain. Start with plunging (other side sealed), then clean the P-trap and snake the trap arm. It’s a classic double-basin symptom, not two separate clogs.
How do I keep it from clogging again?
Keep grease, oil, coffee grounds, and fibrous scraps out of the drain and disposal, run cold water while the disposal runs and for a few seconds after, and flush the drain with hot water and dish soap weekly. See our guides to preventing future clogs and the most common kitchen sink problems. The same buildup habits also clog a bathroom sink — here’s unclogging a bathroom sink if that one’s slow too.