Key takeaways
- Find out whether the blockage is local or further down the line before you do anything.
- Hot water clears grease; a plunger only works if the other opening is sealed.
- Cleaning the trap by hand works on most bathroom clogs and costs nothing but a bucket.
- Baking soda and vinegar freshen a drain; they do not shift a solid hair clog.
- Chemicals go last, and three signs mean it is time to call a plumber.
Most blocked sinks do not need a plumber, and they do not need a bottle of chemicals either. They need five things tried in the right order, starting with the cheapest and finishing with the one that actually removes the blockage. Here is the sequence, what each step works on, and the three signs that mean you should stop and call someone.
First, find out where it is blocked
Run water in the sink and watch. If the water sits in the basin and drains slowly, the blockage is in the branch under that basin. If another tap in the house is also slow, or water comes up in a shower tray when you run the kitchen tap, the blockage is further down the line and none of the steps below will fix it. In a double sink, block the good side before you do anything - that single step is what makes a plunger work.
Start with hot water and a drop of dish soap
Fill the basin a few inches with the hottest water from the tap and add a drop of dish soap. Pull the plug and let it run. This clears grease and soap scum, which is what most kitchen sinks are actually blocked with, and it costs nothing. Give it five minutes. Do not use boiling water on a plastic trap - hot tap water is enough, and boiling water can soften the joints.
Use a plunger, and block the other opening first
A cup plunger works by pressure, not by magic, and it only works if the water has nowhere else to go. Seal the overflow hole or the second basin with a wet cloth, make sure the plunger cup covers the drain opening, and give it fifteen to twenty short, sharp strokes. Then pull the plunger away quickly on the last one. Bathroom sinks usually clear at this step, because the blockage is hair and soap close to the drain.
Clean the trap by hand
If plunging does not do it, put a bucket under the trap, unscrew the slip nuts by hand, and take the trap off. Wear gloves: what comes out is not pleasant, but it is the blockage itself, sitting in the bend where it collected. Clean the trap, check that the washers are not perished, and put it back with the bevels facing the right way. This is messy and it works on the large majority of bathroom clogs.
If your sink has two basins, the diagnosis is slightly different and worth thirty seconds: why a double sink backs up into the other side. And if you want to stop the next clog before it starts, what baking soda and vinegar actually do is worth knowing.
Baking soda and vinegar: what it can and cannot do
The fizz is carbon dioxide, not pressure, so it will not shift a solid hair clog. What it does well is freshen a drain that smells and loosen light soap film, which makes it a good weekly habit and a poor emergency tool. If you use it, follow with hot water, and never mix it with a chemical cleaner.
A drain snake, fed slowly
A hand snake gets through what a plunger cannot. Feed the cable in slowly with the handle turning, stop when you feel resistance, and let the head work rather than forcing it. Forcing it kinks the cable and can scratch a chrome trap, and you will feel the difference immediately - it stops advancing.
Chemical cleaner: last, not first
Chemical cleaners are harsh on rubber seals and chrome, they generate heat in the pipe, and they are dangerous in a sink with a disposal. They also cannot reach a blockage that is packed solid. If you have tried the steps above and the sink is still blocked, a snake or a plumber is a better next move than a bottle.
| Method | Works on | Watch out for |
|---|---|---|
| Hot water and dish soap | Grease and soap scum | Do not use boiling water on a plastic trap |
| Cup plunger | Clogs near the drain | Seal the other basin and the overflow first |
| Cleaning the trap | Most bathroom clogs | Bucket underneath, and check the washers |
| Baking soda and vinegar | Smells and light film | Not a solid clog, and never mix with chemicals |
| Drain snake | Deeper clogs | Feed slowly; forcing it kinks the cable |
| Chemical cleaner | A last resort | Damages seals, and dangerous with a disposal |
Three signs to call a plumber
Stop and call someone if more than one fixture in the house is slow, if water appears in a floor drain or shower tray, or if the sink clears and blocks again within a day. Those point at the main line, a blocked vent or a full septic tank, and no amount of plunging will change them.
The bottom line
Hot water, plunger with the other opening sealed, the trap by hand, then a snake - and chemicals last, if at all. Most household blockages give up at step two or three, and the cheap steps cost you nothing but twenty minutes.
Related reading
- Why does my double kitchen sink back up into the other side?
- Does baking soda and vinegar really unclog a sink?
- Do chemical drain cleaners damage your pipes?
The cheapest way to avoid the next clog is a strainer that catches hair before it reaches the trap: the one we make is our pop-up sink drain stopper with a hair catcher.