How to clean a sink trap and unblock a slow drain yourself

Weekend DIY #4 · Every Saturday a new DIY job in and around the house 

Gurgle, gurgle... and the water just stays there. A washbasin or shower that drains slower every week is one of the most common little annoyances in the house. Most of the time the cause sits only a few centimetres below the plug: hair, soap residue and dirt caught in the trap. In this fourth edition of Weekend DIY we show you how to clean a washbasin trap step by step, how to get the hair out of a shower drain from the top, why you're better off without a chemical drain unblocker, and how to keep the drain flowing afterwards. With the time needed, the difficulty, a materials list and safety tips.

Why does your washbasin or shower drain slowly?

Under almost every washbasin, sink and shower there is a trap: a bend or cup in the waste pipe that always holds a little water. That water forms a seal that keeps the smell of the sewer out of your home (read more about how this was invented in the history of the toilet and the sewer). The downside: everything that goes down the plughole passes through that bend. Hair, soap residue, toothpaste, fat and bits of dirt stick together there, and the water drains a little slower every week. A drain that suddenly smells can also have a trap that has dried out, for example in a guest bathroom that is rarely used.

Should you use a chemical drain unblocker?

Preferably not. According to the Dutch government, drain unblockers contain sodium hydroxide or sulphuric acid and are very corrosive. If you do use one, wear safety glasses and gloves, follow the instructions on the pack and never mix it with other cleaning products: some combinations release chlorine gas. Manufacturers of traps and drains also warn that aggressive chemicals can attack the seals in your waste. The government advice is therefore to try a strainer, a plunger or unscrewing the trap first. According to Dutch environmental guidance, leftover unblocker goes into the residual waste together with its packaging, never down the drain. Have you already poured some in? Then the water in the trap is corrosive: let it work as described on the pack, rinse well with water and wear gloves and safety glasses before you open anything.

Can you unblock the drain with a plunger first?

Yes, that's the first thing to try. Fill the washbasin with a few centimetres of water, place the plunger over the plughole and pump firmly a few times. Most washbasins have an overflow, the small opening at the top of the basin. Cover it with a wet cloth and your hand, otherwise the pressure escapes through the overflow instead of pushing the blockage away. Does the water drain properly again? Then you're done. Is it still slow? Then the dirt is stuck in the trap and it's time to open it up.

What do you need to clean a trap?

• A bucket to put right under the trap
• Waterproof gloves, because the water in the trap is dirty
• An old towel or cloth for the bottom of the cabinet and to cover the overflow
• A screwdriver for a shower grid or a plug with a screw
• Water pump pliers and a cloth, only for a stuck metal nut (not sure which pliers you need? Read which pliers to choose)
• A lamp to see into the cabinet and the wall pipe
• An old toothbrush or a bottle brush for the inside of the trap
• Long tweezers or a thin hook for hair in a shower drain
• A plunger for the first attempt

Step by step: how do you clean a washbasin trap?

1. Clear out the cabinet under the washbasin and lay an old towel on the bottom. Put on your gloves.
2. Put the bucket right under the trap. There is always water in the trap, and it comes out as soon as you loosen it.
3. Take out the plug if it comes out: many plugs can be pulled up or unscrewed. There is often a surprising amount of hair wrapped around it. Clean it in the bucket.
4. Find out which trap you have. A bottle trap has a round cup at the bottom that you unscrew by hand, anticlockwise. A tube trap is a bent pipe with a nut on both sides: loosen both nuts and take the bend off.
5. Turn plastic nuts by hand. Only use water pump pliers on a stuck metal nut, with a cloth between the jaws so you don't damage the finish.
6. Empty the trap into the bucket and scrub the inside clean with an old toothbrush or bottle brush. Rinse the parts in the bucket or another basin, not in the washbasin you're working on: with the trap off, the water runs straight into the cabinet.
7. Shine a lamp into the wall pipe and remove any dirt you can reach.
8. Check the rubber rings and seals. Is a ring cracked, hard or flattened? Replace it with a matching one. Take the old ring with you, so you get the right size.
9. Put everything back together. Make sure every ring sits straight and screw the nuts back on by hand. Manufacturers of traps advise no tighter than hand-tight plus a quarter turn: if you tighten plastic too hard, it can crack or the ring can get pushed out of place.
10. Run water and check for leaks. Let the tap run fully for a minute and feel under every connection with a dry piece of kitchen paper. Check again after an hour.

Step by step: how do you clean a shower drain from the top?

1. Remove the grid or cover of the shower drain. Some lift straight out, others are held by one or two screws.
2. Take out the hair catcher or inner cup if your drain has one. In many shower drains it turns out anticlockwise.
3. Remove the hair and dirt with your gloved hand, long tweezers or a thin hook.
4. Rinse the loose parts in the bucket and scrub away soap residue. Be careful with any rubber O-ring: if it gets damaged, the water seal no longer closes properly.
5. Put everything back in the right order and run the shower for a minute to check that the water drains well again.

What should you look out for when it comes to safety?

• Wear gloves: the water in a trap is dirty, and may still contain unblocker.
• Wear safety glasses if a chemical unblocker has been used, and never mix cleaning products.
• Ventilate the bathroom while you work, especially if you use a cleaner.
• Keep children and pets away from the bucket and from any cleaning products.
• Pour the dirty water down the toilet and put solid dirt and hair in the residual waste.

How do you prevent your drain from blocking again?

• Use a strainer or hair catcher in the washbasin, the sink and the shower drain.
• No fat or frying oil down the drain. According to the Dutch water boards, fat solidifies and sticks to the pipes. Wipe pans with kitchen paper first.
• No wet wipes down the drain or the toilet, and put food scraps in the organic waste.
• Run water regularly in a washbasin or shower that is rarely used, so the trap doesn't dry out and start to smell.
• Clean the trap now and then, before the water starts draining slowly.
• Clean the overflow with a cleaner based on acetic acid or citric acid, as manufacturers advise. Is your tap full of limescale too? Read how to descale a tap and clean the aerator.

When is it better to call a plumber?

Is the drain still blocked after the plunger and a clean trap? Then the blockage is further down the pipe, and that's a job for a plumber. Manufacturers also advise against high-pressure drain cleaners, because they can damage traps. Call a plumber too if a trap keeps leaking after you've put it back together, or if you can't reach the trap without taking things apart.

Which Saniso products do you need for this job?

The basics are a bucket, waterproof gloves and a screwdriver set. With a work lamp you can see what you're doing under the washbasin, and the pliers are only needed for a stuck metal nut.

How do you order at Saniso if you're not a customer yet?

Your first order is easy to place:

1. Create an account via register.
2. Already have an account? Log in here with your email address or phone number.
3. Choose your product and click "Add to cart" or go straight to "Buy now".
4. Check out and choose home delivery or pick-up in our showroom.

Still have questions about ordering?

Questions about ordering, your account, payment, shipping or returns? Find all the answers in the Saniso FAQ.

Frequently asked questions about cleaning a trap

Weekend DIY: every Saturday morning a fun, doable job in and around the house. Missed an earlier one? Read how to reseal your bathroom with new silicone. Next Saturday brings a new job.