Quick Answer:
If the sink suddenly fills while you’re washing dishes, stop running water immediately and bail out any standing water to prevent overflow damage. Try a quick plunge and listen—if the water only drains slowly or you hear gurgling, you probably have a partial clog. For related situations see Sink backs up with no warning.
Why This Happens
- Grease, food scraps, or soap build up over time and can suddenly block the drain when a soft blockage shifts.
- Items like utensils or small dishware can slip past the strainer and lodge farther down.
- Shared drain lines (double bowls) or a partial restriction farther down the line can let water back up quickly when flow increases. If this happens during heavy cooking or washing large pots, also see Overflow during heavy cooking.
Step-by-Step What to Do
1. Stop the flow and remove standing water
- Turn off the tap immediately.
- Use a small container or cup to bail water into a bucket. The less water that spills onto the floor or cabinet, the better.
2. Check for visible obstructions
- Remove the sink strainer or stopper and clear any visible debris near the drain opening.
- If you can reach the obstruction safely (gloves on), pull it out rather than pushing it further down.
3. Listen and observe the drain
- Put the stopper back and run a small amount of water briefly, then stop. Listen for gurgling or a slow drop—these are clues of a partial clog.
- If the water level falls slowly or not at all, note that the restriction may be downstream of the trap.
4. Test the other bowl if you have a double sink
- Fill the other bowl slightly and then let it drain. If both bowls rise together, the blockage is likely beyond the shared drain or in the main line.
5. Try a plunger next
- Use a cup plunger (not a flange toilet plunger). Seal around the drain and plunge with steady, even strokes for 15–30 seconds.
- After plunging, run a little water to see if drainage improves. If water still won’t drop, the restriction is likely downstream of the trap or in the house drain.
6. When to avoid more DIY
- If standing water doesn’t drop after these steps, or if the drain smells strongly of sewage, stop and call a professional. Removing traps or using powered tools can be messy and may worsen the problem if you’re unsure.
What Not to Do
- Don’t keep running water to “push it through”—overflow water damage adds up fast.
- Don’t pour large amounts of chemical drain cleaner into standing water. It can be ineffective on physical blockages, damage pipes, and present a hazard if a plumber needs to work on the drain.
- If the sink won’t drop quickly, a plumber is appropriate rather than continued DIY attempts that could cause more damage.
When to Call a Professional
- Standing water remains after plunging and simple clearing.
- Both bowls back up at once, indicating a main drain or sewer-line issue.
- You smell sewage, hear persistent gurgling in other drains, or notice backups in other fixtures—these suggest a deeper blockage or venting problem.
- There is water leaking from pipes or cabinet flooding—stop attempts and call a plumber to protect structures and electrical components.
Safety Notes
- Wear gloves and eye protection when handling debris or tools.
- Keep electrical appliances and cords away from standing water in the sink or on the countertop.
- Avoid mixing chemical cleaners. If you used any, ventilate the area and don’t use a metal snake or other tools that could react with residues.
- If you’re unsure how to remove the trap or use a drain snake safely, call a professional to avoid injury or damage.
Common Homeowner Questions
- Why did this happen suddenly?
Slow buildup of grease or debris often reaches a tipping point when it shifts or a new object lodges in the line. - What is the fastest thing I can try right now?
Stop the water, bail out standing water, remove visible debris, and try a cup plunger. If it doesn’t clear, call a plumber. - Will a chemical drain cleaner fix it?
Chemical cleaners can be risky with standing water and are often ineffective on solid obstructions; use with caution or call a pro.