Kitchen Sink Blocked: How to Clear It (and When to Stop)

Before you start

Bail out most of the standing water into a bucket. Put on gloves. If you poured any chemical product down the sink, stop here and tell whoever clears it — you do not want that on your hands or in your eyes.

Put a bucket and some cloths under the sink. Take everything out of the cupboard.

Step 1: plunge it

If you have a double sink, block the second drain with a wet cloth or a plug; otherwise the pressure escapes through it. Do the same with the overflow hole.

Leave a few centimetres of water in the sink so the plunger seals. Plunge firmly 10 to 15 times, then pull away sharply. Repeat two or three rounds.

Step 2: clean the trap

The trap unscrews by hand on most modern sinks — a large plastic nut at each end, or a bottle trap with a cup that unscrews at the bottom.

Empty it into the bucket and clean it with an old brush and hot water. Check the rubber washers are in place before screwing it back on hand-tight. Run water and check for drips.

If the dishwasher or washing machine drains into the same trap, check its hose connection too — it can hold food waste.

Step 3: hot water and washing-up liquid

With the trap clean, pour a kettle-warm (not boiling) mix of hot water and washing-up liquid down the drain to soften grease further along. Boiling water can soften plastic pipes and joints.

Why kitchen sinks block in Lisbon

Many older buildings have narrow waste pipes with very little slope. Cooking fat cools and sets inside them, catching food scraps and coffee grounds. Hard water adds limescale. Over the years the pipe narrows until one day it closes.

That is why a sink that "drains a bit slowly" is worth dealing with early: slow draining is a blockage forming.

When to stop and call

If the trap is clean and the water still does not drain, the blockage is in the pipe behind the wall. A hand snake from a shop may reach it; a professional drain snake will.

If the sink blocks again within weeks, the pipe walls are coated in grease. Clearing a hole through it only buys time — drain jetting cleans the whole pipe so it lasts.

If water comes up in the sink when the washing machine drains, or in a neighbour's sink, the shared waste pipe is involved. See gurgling drains.

Keep it from coming back

Never pour cooking fat or oil down the sink. Let it cool and throw it in the bin, or take used oil to a collection point.

Use a strainer in the plug hole, scrape plates into the bin, and do not put coffee grounds down the drain.

Once a month, run very hot tap water with washing-up liquid for a minute. Clean the trap once or twice a year.

Using a hand drain snake

With the trap removed, feed the snake into the pipe that goes into the wall. Turn the handle as you push; when you feel resistance, keep turning to break through or hook the blockage, then pull back slowly and clean the end.

Wear gloves and have a bucket ready. Do not force it round tight bends in old pipes — you can damage the joints.

Dishwashers and washing machines

A dishwasher that does not drain, or leaves dirty water in the bottom, may have a blocked filter (clean it — it is in the bottom of the machine), a kinked hose, or a blocked sink waste where it connects.

If both the sink and the dishwasher are slow, the shared pipe is the problem. See gurgling drains.

Food waste disposers

Waste disposers are uncommon in Portugal, and in older buildings with narrow pipes they can make blockages worse. If you have one, run plenty of cold water while using it and never put fat, fibrous peelings or coffee grounds through it.

What jetting does that a snake cannot

A snake opens a hole through the blockage. Jetting cleans the whole inside of the pipe with high-pressure water, removing the grease layer that makes the next blockage inevitable. For a kitchen that blocks every few months, it is the lasting fix.

Unblocking starts from 75 €; jetting is quoted after seeing the pipe run. See drain jetting.

Frequently asked questions