Blocked sink or drain: how to unblock it yourself

A slow or blocked sink is one of the most common plumbing problems at home. Usually the blockage is close by, in the plug or the water trap, and you can clear it yourself with a bucket and a plunger. This guide shows how to unblock a sink without chemicals, what to do about a blocked toilet, and how to tell when the problem is deeper in the building's drains.

Slow or completely blocked?

A slow sink means hair, soap or grease has started to collect in the trap or the waste pipe. This is the easiest moment to clear it, before the pipe closes up completely. If the water doesn't drain at all, scoop the standing water out of the basin first.

If only one sink is slow, the blockage is almost always in its own trap or waste pipe. If several drains are slow at once, the cause is most likely in the building's drains (see below).

Start with the plug

In a bathroom basin, hair often gets caught on the plug (pohjaventtiili). On many sinks the plug lifts or twists out by hand. Clean it and look into the opening: a visible clump of hair can often be pulled out with a thin barbed plastic strip, sold in hardware stores. In a kitchen sink, rinse the strainer.

How to clean the water trap, step by step

The water trap (vesilukko) is the bend or bottle-shaped part under the sink; the water standing in it keeps sewer smells out of the room. Most blockages are right here, and a plastic trap usually opens by hand. (If the smell comes from the bathroom floor drain, see how to clean a floor drain.)

1. Empty the basin. Scoop any standing water into a bucket with a mug.
2. Protect the cabinet. Clear the cabinet under the sink, put a towel down and place a bucket under the trap.
3. Open the trap. On a bottle trap, unscrew the cup at the bottom. On a tube trap (U-bend), loosen the nuts that hold the bend. There is always water in the trap, so let it run into the bucket.
4. Clean the parts. Remove the hair and sludge and scrub the parts with a brush, but not in the blocked sink.
5. Check the seals. The rubber washers should be undamaged and sit correctly.
6. Reassemble and test. Tighten the parts firmly by hand, without tools. Run water and check the joints with dry paper.

In a kitchen, the dishwasher's drain hose is often connected to the sink trap, so check that this connection is tight too.

Using a plunger the right way

If the trap was clean, the blockage is probably further along the waste pipe. A plunger (imukuppi) works when it pushes water, not air:

• Run enough water into the basin to cover the rubber cup.
• Block the overflow hole with a wet cloth. On a double kitchen sink, plug the other drain too, or the pressure escapes there.
• Press the plunger firmly up and down 10–15 times, then pull it off sharply.
• Repeat a few times and check whether the water drains.

A drain snake, carefully

A drain snake (viemärikierre) is a flexible steel spring turned with a handle. Remove the trap and feed the snake straight into the waste pipe in the wall. Push and turn it slowly, working it gently back and forth when you feel resistance, then pull it out over the bucket. Forcing it can damage an old cast-iron pipe or the joints of a plastic pipe. If it won't go further, leave the job to a professional.

Why not to rely on harsh chemicals

Chemical drain openers are lye- or acid-based and strongly corrosive, and they rarely shift a clump of hair. They also come with risks:

• Used repeatedly, they can damage old pipes, joints and rubber seals.
• Mixing products is dangerous. A chlorine-based cleaner and an acid, for example, can release toxic gas together.
• If the blockage doesn't clear, corrosive water stays in the basin and trap, a danger to whoever opens the trap or plunges next.

If you have already used one, protect your hands and eyes and tell anyone who carries on with the job.

Blocked toilet: the basics

A blocked toilet is usually caused by too much paper, wet wipes or a fallen object. Don't flush again if the water level is rising, and close the toilet's shut-off valve if needed. Paper often softens if the water is left to stand for a while. Use a toilet plunger with a narrower flange, and for a deeper blockage a toilet auger with a sleeve that protects the porcelain.

Don't push a fallen object further in. If it is stuck inside the toilet, the toilet may need to be removed. If the toilet is old or cracked, replacing it may make more sense; see our guide to toilet replacement costs.

Signs the blockage is in the building's drains

The blockage is most likely deeper in the drainage system if:

• several sinks, the shower and the toilet drain slowly at the same time
• the drains gurgle when a toilet is flushed or the washing machine empties
• water rises in the floor drain (lattiakaivo) when you use a sink or the toilet

In an apartment building, avoid using water and contact the maintenance company (huoltoyhtiö). The vertical stacks and main sewer line are shared pipes and usually the housing company's responsibility; the exact split is in the responsibility table, or ask the property manager (isännöitsijä). If you rent, tell your landlord too. In a detached house, the drains are the owner's responsibility. A deep blockage is usually cleared with high-pressure flushing equipment by a company specialising in sewer maintenance.

When to call a plumber

Ask a plumber to take a look when:

• the trap is cracked or leaks after you have reassembled it
• the same sink keeps blocking even after the trap has been cleaned
• the plug is broken and no longer holds water
• the sink or the toilet itself is damaged

A new trap or plug can be fitted as one of our small plumbing jobs. If the sink is cracked or you want a new one, see sink installation and replacement; the work costs €156.88–235.31.

Preventing blockages

• Wipe greasy pans with kitchen paper before washing up. Larger amounts of cooled fat go in the rubbish according to local sorting rules.
• Coffee grounds and food scraps go in the biowaste. Grounds pack into a dense sludge in the pipes.
• Only toilet paper goes in the toilet. Wet wipes and cotton buds don't break down like paper.
• Use a hair catcher in the shower and the basin.

Summary

Most blocked sinks clear once the plug and the water trap are cleaned, helped if needed by a plunger or a gently used drain snake, with no harsh chemicals. If several drains are slow or water rises in the floor drain, contact the maintenance company. If a trap, plug or sink needs replacing, contact us to arrange the work.