Quick Answer:
If the disposal runs but the sink drains slowly and smells like grease, start by wiping greasy residue from the disposal baffle and flush with cold water. Avoid hot water (it can re-melt grease and smear it further). If slow drainage and odor persist after cleaning the trap and immediate piping, the clog is likely farther down the branch and will need deeper cleaning or professional help.
Why This Happens
Grease and cooking fat behave differently from food scraps. When hot, grease is liquid and can travel down the drain; as it cools it re-solidifies and sticks to the sides of the disposal throat, tailpiece, or branch drain. Over time that coating narrows the pipe and traps small bits of food, causing a slow drain and a persistent odor even though the disposal motor still runs.
Minor buildup is often at the disposal baffle and trap. More stubborn clogs live farther down the branch line and sometimes require removing the trap or cleaning the branch pipe. If you need more context on similar problems, check the related topics such as Sink backs up after disposal hums and Disposal works but water drains into other bowl.
Step-by-Step What to Do
1. Clear the immediate area and turn the unit off
- Cut power to the disposal at the wall switch and/or unplug it.
- Remove standing water from the sink so you can see into the drain.
2. Wipe the disposal baffle
- Use a paper towel or rag to wipe any visible greasy residue from the rubber baffle and upper throat. Grease on the baffle holds odors and collects debris.
- Dispose of the greasy towel in a trash bag—don’t rinse it down the sink.
3. Flush with cold water
- Run a steady stream of cold tap water for 15–30 seconds while running the disposal briefly to flush loosened material. Cold water helps solidify grease so the disposal can chop and move small pieces rather than smear them.
4. Check and clean the P-trap
- Place a bucket under the trap, loosen the slip nuts, and remove it to check for gunk. Clean the trap with a brush and cold water.
- Reinstall carefully, hand-tighten nuts, and test the drain.
5. If slow drain or smell remain, clean the branch
- Persistent odor and slow drainage after trap cleaning usually means buildup farther down the branch. A manual snake or plumber’s auger may be needed to break up that grease lining.
- If you’re not comfortable snaking the pipe, or if snaking doesn’t help, call a professional.
What Not to Do
- Don’t use hot water and soap as a grease fix—this can move grease farther and re-solidify lower in the pipes, making the problem worse.
- Don’t stick your hand into the disposal or use metal tools inside while it’s connected to power.
- If grease clog remains, a plumber is appropriate—don’t keep trying harsh DIY fixes that could damage pipes or the disposal.
When to Call a Professional
Call a plumber if:
- Cleaning the baffle and trap doesn’t clear the slow drain or smell.
- Snaking the branch line fails to remove the buildup or you encounter resistance that won’t yield.
- You suspect the clog is deep in the branch line or near the main, or if repeated clogs occur after cleaning.
A pro can remove and clean deeper sections of pipe, use a long auger, or perform a hydro-jet when appropriate.
Safety Notes
- Always disconnect power to the disposal before reaching into or working on it.
- Use gloves and eye protection when handling greasy parts or working under the sink.
- Don’t mix chemical drain cleaners with other products; they can react dangerously and often do not remove grease lines effectively.
Common Homeowner Questions
- Why did this start if the disposal still runs? The disposal chops scraps, but it doesn’t dissolve grease; grease adheres to pipe walls and causes slow drains over time.
- Will pouring boiling water clear it out? No. Boiling or hot water can melt grease and push it farther down where it re-solidifies and worsens the clog.
- Can I prevent it from returning? Yes. Avoid pouring grease down the sink, wipe pans with a paper towel before washing, and rinse with cold water while running the disposal after small scraps.