Quick Answer:
Grease from cooking can cling to pipe walls and trap food particles, making a kitchen sink drain slower after meals. Start by noticing exactly when the slowdown happens, clear the strainer and trap, use mechanical tools before chemicals, and change how you discard grease to prevent it returning.
Why This Happens
Oils and fats are liquid when hot but can cool and stick to the inside of pipes. Each time you pour oily water down the sink, a thin film can build up. Over weeks or months that film traps food scraps and soap scum and narrows the flow. If the slowdown follows meal prep or greasy dishwashing, grease buildup is a likely cause.
Step-by-Step What to Do
1. Note drainage behavior after cooking sessions
- Watch when the drain slows: immediately after cooking, after the water has cooled, or only after several uses. Record whether it happens only on heavy-grease days.
- Try a simple test: run water at full flow for 30 seconds into the sink and time how long it takes to clear. Repeat after a greasy meal and when the sink is clean to compare.
2. Remove and clean the strainer or stopper
- Clear visible debris and wipe away greasy residue with paper towels (dispose in trash, not down the drain).
- Rinse the strainer with hot soapy water to remove oil and trapped food.
3. Plunge the sink
- Use a cup plunger (cover any overflow or second basin) and plunge firmly for 15–30 seconds to dislodge soft blockages.
- Test the drain after plunging and repeat if needed.
4. Check and clean the P-trap
- Place a bucket under the trap, loosen the slip nuts, and remove the trap to clear trapped grease and solids. Clean with a brush and wipe out oil with paper towels.
- Reassemble and test the drain. Tighten connections to avoid leaks.
5. Use a drain snake for deeper clogs
- Feed a manual auger or drain snake into the drain to pull out or break up greasy buildup further down the line.
- Work gently to avoid damaging older pipes.
6. Preventive habits
- Let grease cool and solidify in a container, then throw it in the trash or compost where allowed.
- Wipe pans and dishes with a paper towel before washing to remove excess oil.
- Run hot (not boiling) water and detergent after greasy use, and occasionally use a baking soda and vinegar rinse followed by hot water to help lift residue.
What Not to Do
- Do not pour grease down the drain — even small amounts add up.
- Do not rely on boiling water alone. Boiling water can damage some pipes and often doesn’t clear hardened grease deep in the line.
- Avoid frequent use of harsh chemical drain cleaners; they can harm pipes and are dangerous to handle.
When to Call a Professional
- The sink remains slow after you’ve cleaned the strainer, P-trap, and used a snake.
- Multiple drains are slow at the same time or you notice sewage smell or backups.
- Water is standing in the drain for a long time, or you see signs of leaks or corrosion when inspecting pipes.
Safety Notes
- Wear gloves and eye protection when handling drain tools or removing the P-trap. Grease and trapped food can be unpleasant and slippery.
- If you use a baking soda and vinegar rinse, do not mix it with chemical cleaners already in the drain.
- When in doubt about pipe condition or persistent backups, stop and call a licensed plumber to avoid causing more damage.
Common Homeowner Questions
Kitchen sink slow only in morning
Often this happens when grease cools and firms overnight or when a partially blocked vent slows drainage until water use warms and clears the line; check leaks and try a trap clean and snake before calling a pro.
Kitchen sink slow but bathroom fine
This usually points to a local kitchen issue—grease, trap blockage, or a problem with the sink’s tailpiece—rather than a main drain problem affecting the whole house.
Will pouring boiling water clear greasy buildup?
No. Boiling water alone is unreliable and can harm some pipes; use mechanical cleaning and prevention instead, and combine hot water with other cleaning steps if needed.