To unblock a bathroom basin, start at the plughole: take the plug out and clear the hair and gunk off it, then plunge with the overflow covered, and if that does not work, take off the trap under the basin and clean it out. Most basin blockages sit within easy reach of the plughole, so you rarely need chemicals, and you should never use them before plunging or opening the trap.

What you need

• a bucket or washing-up bowl that fits under the basin
• rubber gloves and an old towel
• a small cup plunger (keep it separate from the toilet plunger)
• an old toothbrush or bottle brush
• a plastic hair removal strip or a small hand drain snake
• a torch

Clear the cupboard or space under the basin before you start, and put the towel down. There is always more water in the trap than you expect. If you would rather not take anything apart, our blocked sinks and drains service will clear it for you.

Step 1: Take out and clean the plug

Most modern basins have one of two types of plug.

Click-clack (push-button) plugs

Press the plug down to open it, then unscrew the top anticlockwise. Some lift straight out and some unscrew fully from the spindle. Pull off the hair and slime, clean the spindle and the crosspiece in the waste with the toothbrush, and refit it.

Lever-operated pop-up plugs

If your plug is raised and lowered by a rod behind the tap, look under the basin. A horizontal rod goes into the back of the waste pipe, held by a small nut. Loosen that nut, pull the rod back slightly, and the plug will lift out from above. Clean it, drop it back in, push the rod through the loop or hole on the plug’s tail, and retighten the nut by hand.

Run the tap. If the water now drains freely, you are done. Plenty of basin blockages go no further than this.

Step 2: Clean the overflow

The overflow channel behind the basin collects slime that restricts the flow and causes smells. Push a narrow bottle brush or flexible cleaning brush into the overflow hole, work it around, then rinse with hot tap water. On some basins with a slotted waste, the overflow drains through slots in the side of the waste body, and those slots need clearing too.

Step 3: Plunge it properly

A plunger only works if the pressure has nowhere to escape.

1. Hold a wet cloth firmly over the overflow hole, or ask someone else to.
2. Run enough water into the basin to cover the rubber cup of the plunger.
3. Put the plunger over the plughole with the plug removed, and make sure the cup seals all round.
4. Push down gently to expel the air, then pump firmly up and down a dozen or so times without breaking the seal.
5. Pull the plunger off sharply and see if the water drains.

Repeat two or three times. If the water level drops a little each time, keep going. If nothing changes, move on to the trap.

Step 4: Remove and clean the trap

The trap is the bend or pot under the basin that holds water to stop drain smells coming up. Bathroom basins normally have either a bottle trap (a straight pot with a removable base) or a tubular trap (a U or P shaped bend).

1. Put the bucket directly underneath.
2. For a bottle trap, unscrew the base of the pot by hand. For a tubular trap, unscrew the two large nuts, one at the waste and one at the outlet.
3. Let the water drain into the bucket, then pull out the hair and sludge. Rinse the trap in the bucket, not in the basin you are trying to clear.
4. Check the rubber washers or sealing rings are still in place and not split.
5. Refit the trap hand tight. Plastic threads crack if you use grips on them.
6. Run the tap for a minute and check for drips under the trap.

If you cannot unscrew it by hand, or it looks brittle or cracked, leave it for a plumber rather than forcing it.

Step 5: Use a drain snake past the trap

With the trap off, you can see into the waste pipe that runs to the wall. A small hand drain snake can be fed into that pipe to pull out hair or break up a blockage further along. Feed it in gently, turning the handle as you go, and do not force it round tight bends. Pull it back slowly and clean it into the bucket.

If the blockage is further than you can reach, or the bath and shower are also slow, the problem is in the shared waste or the soil stack, and that needs a plumber. Our guide to a slow draining basin explains how to tell where the problem is, and a plumber can clear it with longer tools.

What not to use

Method	Our view	Why
Boiling water	Avoid	Can soften plastic waste fittings and loosen joints, and does not dissolve hair
Chemical drain unblocker	Last resort only	Harsh on seals, dangerous if it splashes, poor on hair mats, and it makes opening the trap risky
Bicarbonate of soda and vinegar	Fine as a freshener	The fizz looks busy but it does not break down hair
Wire coat hanger	Avoid	Scratches the waste, can pierce flexible pipe and pushes blockages further in
Hot tap water with washing-up liquid	Worth a try for soap build-up	Helps loosen soap and grease but will not clear hair
Toilet plunger	Avoid	Too big to seal on a basin, and unhygienic

How to stop the basin blocking again

• Pull hair off the plug every week or two. It takes seconds.
• Fit a plughole hair catcher if you have long hair in the house.
• Run the hot tap for a minute after shaving or brushing teeth.
• Never rinse tile grout, filler, plaster or paint down the basin. It sets in the trap.
• Keep cotton buds, dental floss and wipes out of the basin and the toilet. See our list of items that should never go down your drain.

If your shower is slow too, our guide on how to unblock a shower drain follows the same principles.

What it costs with Vantage

In normal working hours there is no call-out fee. After the first hour, time is charged in half-hour steps, and parts such as a new trap or waste are quoted before we fit them. Evening, weekend and overnight visits are charged at the out-of-hours rates. Every rate is published on our prices page, so you know what you will pay before we arrive.

Frequently asked questions

Can I unblock a basin without a plunger?

Yes. Take out and clean the plug, then remove and clean the trap. Those two steps clear most basin blockages without any plunging. A plastic hair removal strip, sold in most DIY stores, is also good at pulling hair out of the waste.

Why does my basin still drain slowly after cleaning the trap?

The blockage is further along the waste pipe, or the pipe has too little fall and collects debris. It can also be a partly blocked shared waste or stack if other fittings are slow too. A plumber can clear it with a longer snake and check the pipe.

Is it safe to pour boiling water down a bathroom sink?

It is best avoided. Boiling water can soften plastic waste fittings and loosen push-fit joints, and it does nothing to hair. Hot water from the tap is safe and helps with soap build-up.

How do I stop my trap leaking after I refit it?

Check each rubber washer is in place, seated flat and not split, and that the threads are not cross-threaded. Tighten by hand only. If it still drips, the washer or the trap needs replacing.

Can a blocked basin be a sign of a drain problem?

Yes, if the bath, shower or toilet are also slow or gurgling, or an outside gully is overflowing. In that case the blockage is below the basin, possibly in the underground drain, and plunging the basin will not fix it.

Blocked basins cleared across Hertfordshire, Bedfordshire and Cambridgeshire

If you have tried the steps above and the basin is still blocked, or you would rather not take the trap apart yourself, our engineers clear basin and sink blockages in Buntingford and right across Hertfordshire, Bedfordshire and Cambridgeshire. See our blocked sinks and drains page, or call 01462 506374. The phone is answered 24 hours a day, 7 days a week.