How to unblock a kitchen sink without harsh chemicals

15 to 45 minutes. Costs nothing to a few dollars.

Try this first (costs nothing): pour a kettle of very hot, not boiling, tap water down the drain and wait a few minutes. A block of grease often melts and moves. Do not do this if your pipes are plastic and the maker warns against it. Check first.

This page covers how to unblock a kitchen sink in order: free, cheap, then call a plumber.

Step 1: Plunger

1. Take out the plug and fill the sink with a few centimetres of water.
2. Block the overflow hole with a wet cloth, or the plunger loses suction.
3. Put the plunger over the plug hole and push down and up with steady strokes, ten times.
4. Pull off sharply. Watch the water.

If the sink has two bowls, block the other drain with a cloth too.

Ruling: a plunger clears most soft blocks. Try it three or four rounds.

Step 2: Clean the U-bend

The U-shaped pipe under the sink collects grease and food.

1. Put a bucket under it. Wear gloves.
2. Unscrew the nuts by hand. If tight, use a cloth and a spanner.
3. Tip out the water and clean the inside with an old brush.
4. Put it back, make the nuts snug, and run the tap to check for leaks.

Ruling: this is the most common fix once the plunger fails.

Step 3: Drain snake

If the block is past the trap, feed a plastic drain snake into the pipe, turn and pull it back. Wash it after. Do not force it, because you could scratch a pipe.

Ruling: a snake solves hair or food stuck deeper in the pipe.

Chemical cleaners

Use one product at a time. Never mix cleaners. Drain cleaners are strong, they can hurt skin and eyes, and they may harm some pipes. Read the label. If you do use one, wear gloves, open a window and follow the label. A poison centre can advise if you spill or inhale one. A plumber cannot work safely in a sink full of strong chemicals either, so tell them if you used one.

If that does not work

• More than one sink or the toilet gurgles: the block is in the main drain. Call a plumber.
• Slow all the time: pipes may be narrow or damaged. Call a plumber.
• Smell: see fridge smell fix if it is also in the kitchen, but drain smells need a trap clean.

For the tool choice, see plunger vs drain snake.

Worked example

Say the sink drains in ten minutes instead of two. Round numbers. You pour hot water, no change. You plunge ten times, a little better. You clean the U-bend and find a greasy clump the size of a golf ball. After refitting, the sink empties in seconds. The whole job takes about 30 minutes.

Common mistakes

• Pouring fat down the sink. It cools and sticks.
• Using a plunger without blocking the overflow.
• Mixing cleaners.
• Overtightening the U-bend nuts.

Fix it, replace it or live with it

Fix it with the ladder above. Replace pipes only on a plumber's advice. Do not live with a slow sink, it gets worse.

What clogs a kitchen sink

Grease is the main cause. It looks liquid when hot and sets into a paste as it cools in the pipe. Coffee grounds, rice, pasta and potato peel add to it. A food strainer in the plug hole catches most of this. Scrape plates into the bin before washing.

Keep it clear

• Wipe greasy pans with paper before washing.
• Pour cooled fat into a jar, then into the bin.
• Run hot water after washing up.
• Use a strainer and empty it daily.
• Clean the U-bend a couple of times a year if the sink is slow.

Where the answer flips

If you rent, tell the landlord, since pipes and drains may be their job. If the sink backs up into a dishwasher or washing machine, stop using them and call a plumber. A bad smell from the drain with no block usually means a dry or dirty trap. Pour a little water down to refill the trap and clean it.

What to have in a drawer

A flat-cup plunger, a plastic drain snake, a bucket and gloves cost very little together. Keep them somewhere easy to reach. A sink strainer helps. A small torch helps when you are looking under the sink.

Tips for the U-bend job

Put a towel under the bucket to catch drips. Take photos before you unscrew, so you can put it back the same way. Keep the washers (the rubber rings) in order. If a nut is stuck, do not force it, since plastic pipes crack. Try a cloth for grip. If it still will not move, stop and call a plumber.

What a plumber will likely do

A plumber may use a powered tool or a camera to find the block. Tell them what you have tried, and whether you used a chemical cleaner. That keeps them safe. A callout fee is usually worth it if the sink is not your own to repair or if more than one drain is slow.