Short answer: Most kitchen clogs are grease, coffee grounds and food scraps stuck in the P-trap or in the pipe inside the wall. If only one side of a double sink is slow, the clog is in that side or the disposal. If both sides are backed up and the P-trap is clear, the clog is further down the line and a drain snake or a plumber is the next step.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| One side slow, the side with the disposal | Disposal jammed or drain outlet clogged | Run the disposal; check for humming | Rarely |
| Both sides backed up | Clog in the shared trap or branch line | Remove and check the P-trap | If past the trap |
| P-trap is clear but water still backs up | Clog in the pipe inside the wall | Use a hand snake through the wall pipe | Often |
| Kitchen and other drains slow | Main line problem | Check other sinks and toilets | Yes |
| Dishwasher water backs into the sink | Clog in the sink drain or disposal | Clear the sink drain first | If it continues |
What to try first
- Turn off the disposal and the dishwasher.
- Use a cup plunger on the clogged side; if you have a double sink, cover the other drain with a wet rag or a stopper so the pressure goes to the clog.
- Run hot water for a minute; it can loosen grease, but do not pour boiling water into a sink full of standing water or into plastic pipes repeatedly.
- If the disposal side is slow, see our garbage disposal guide.
Checking the P-trap
Put a bucket under the trap, loosen the two slip nuts by hand and remove the curved section. Clean it out and reinstall it, making sure the washers sit correctly so it does not leak or smell. If the trap was clear, the clog is in the pipe beyond it.
Clog past the P-trap
A hand snake (drain auger) fed into the pipe going into the wall can reach clogs a few feet away. If that does not work, or if other drains are also slow, the problem is further down and a plumber should clear it. Avoid mixing chemical drain cleaners with a plunger or a snake: splashing drain cleaner causes burns.
When to call a professional
- Water does not go down after plunging and clearing the trap.
- Other drains in the house are slow or gurgle.
- You have already used a chemical drain cleaner (tell the plumber).
- The pipe under the sink leaks or is corroded.
What it usually costs
HomeGuide (2026) lists unclogging a drain at about $100 to $275 and plumbers at $45 to $150 per hour, plus a call-out fee in many areas.
Frequently asked questions
Why are both sides of my kitchen sink clogged?
Both sides drain into the same pipe. If both are backed up, the clog is in the shared part of the trap or further down the branch line.
Does baking soda and vinegar unclog a drain?
It can help with light buildup and odors, but it rarely clears a real grease or food clog. Mechanical methods (plunger, trap cleaning, snake) work better.
Related problems
- Garbage disposal not working
- Clog deep in the drain pipe
- Shower drain clogged
- Sewer smell in the house
Sources
- InSinkErator: Fixing a jammed garbage disposal
- HomeGuide: Plumber cost per hour (2026)
- Oatey: Sewer gas odor in your house and what to do about it
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.