How to unblock a sink - and what you should never pour down your drain

A blocked sink is one of those household headaches that always seems to strike at the worst possible moment. Whether it’s a slow drain or a complete clog, knowing how to fix it quickly can save you time, money and frustration.

But prevention is just as important as cure – and some common kitchen and bathroom habits might be causing more harm than you realise.

Be inspired to make home improvements. 

What are the signs your sink is blocked?

Spencer said there are three key signs your drain might be getting clogged:

Smells A glugging sound The water drains more slowly 

How to unblock a kitchen sink

When faced with a blocked kitchen sink, it’s best to start with the simplest solutions first.

Use with a plunger:Try a :unscrew the trap  or U-bend 

Before you start, place a bucket or bowl underneath the U-bend to catch any water or debris. Have protective gloves and a towel handy.

'The trap is designed to have water sitting in it all the time,' said Spencer. 'It acts as a seal to prevent unpleasant odours. So you need to put a bucket underneath it to catch the water.'

To clear out the trap, do the following:

Locate the trap directly below the sink.

Using your hands (or a spanner for tight fittings), carefully unscrew the connectors on either side of the trap.

Pour out any water in the trap and remove built-up debris, such as food particles, grease or hair. Use a bottle brush or old toothbrush for a thorough clean.

Rinse the trap with warm, soapy water to remove any remaining residue.

Reattach the trap securely, ensuring all connections are tight, to avoid leaks. Run water through the sink to check for proper drainage and confirm there are no leaks around the trap.

How to unblock a sink with water in it

If your sink has become so clogged that water has stopped flowing altogether, use a cup or small container to bail out as much water as possible into a bucket or bowl.

Then, as before, place a bucket or bowl below the U-bend and unscrew the trap and clean. Again, keep an old towel to hand in case of a sudden gush of water.

When do you need to get expert help?

If you've removed and cleaned the trap and U-bend, but the drain remains blocked, it may be time to call in a professional.

Spencer suggests you look for a drainage engineer or a plumber who also specialises in drainage issues. ‘A lot of people assume you need a plumber but although several plumbers do clear drains in addition to doing installations, a drainage expert is often the better choice for specialised drain problems,' he said.

A drainage expert may use cameras or sonic tracking devices to identify blockages deeper within the pipes and then employ high-pressure jets to clear them. Spencer says you shouldn't attempt to do this yourself, and instead seek expert help.

Find a Which?-endorsed drainage expert or plumber through , or use the tool below.

How to unblock a bathroom drain

Bathroom drains typically become clogged with hair, soap scum and non-biodegradable materials that have been flushed accidentally, such as wipes or sanitary products.

To start, pour 500ml of hot tap water down the drain. If this doesn't drain away, use a plunger to force it through.

Then, take your unblocker of choice and, following the instructions, pour it down the shower drain and leave it for the amount of time the manufacturer recommends.

Afterwards, pour another 500ml of hot tap water down the drain.

As with any bleach-based products, make sure you always wear gloves and old clothes, and follow the instructions carefully.

Giving the rest of your shower a deep clean? See  and  to get the whole area sparkling.

Five everyday drain unblocking tools you need

You never know when a drain is going to get clogged up, so it's always good to have a few essentials in your cleaning arsenal, including:

Plunger Drain unblockerDrain protectors Enzyme cleaning sticks A hair snare or drain snake  Take these simple steps to reduce your household's impact on water pollution.

Do home remedies work for unblocking sinks?

Some homeowners use a mixture of baking soda and vinegar to tackle blocked drains.

‘Home remedies may tackle some of the smell of a blocked drain, but they're not strong enough to help with a drain that is really clogged,’ said Spencer.

We tested this for ourselves and proved Spencer right. While the mixture fizzed in the plughole, it wasn't enough in any of our attempts to remove a hairball.

Can you pour oil down the sink?

Fats, Oils, and Grease

Water company Severn Trent said it had cleared the equivalent of six Olympic-sized swimming pools of FOG last year, plus 28,782 blockages caused by incorrect items being put down toilets and sinks.

Over time, some of these materials congeal and create blockages, known as fatbergs, which can lead to severe disruptions in wastewater flow. Instead:

Kitchen tools such as mini spatulas can be handy for scraping plates and containers before washing them.

Collect used cooking oil, fat and grease into a container and put it in the bin once cool. 

 You can reuse cooking oil a handful of times, but you do have to make sure you don't overheat it, and you should still dispose of it regularly. This is because each time it's heated, it creates harmful compounds. If you overheat or burn the oil, this happens quicker.

Don’t use oil you’ve used to fry meat or fish for other foods, to avoid cross-contamination. Strain the oil, keep it in a clean glass jar or stainless steel container and dispose of it as above after three uses.

Can you pour beer down the sink?

Pouring beer down the sink occasionally and in small amounts is generally harmless.

However, avoid disposing of large quantities regularly. This could lead to potential issues like clogging or bad odours over time, because beer contains sugars, yeast, and other organic matter that can build up.

Can you pour bleach down the sink?

Some people use bleach to clean toilets and bathroom sinks, but there are certain things you should be wary of when using it.

Household bleach in the UK is usually sodium hypochlorite-based and is effective at killing germs and disinfecting when used properly. It can also help eliminate odours. But it's essential to know how to use bleach safely before cleaning with it.

It's a highly corrosive substance, so you shouldn't leave it sitting undiluted in the toilet bowl for more than a few minutes – check the instructions for how long.

It can also react with other cleaning solutions, particularly acid-based products like limescale removers and vinegar, which risks creating toxic gas. It can even react with the ammonia found in urine, so it's important to flush the toilet before and after cleaning it with bleach to reduce this risk.

If using bleach to clean your sink, follow the instructions and, as with your toilet, don’t leave undiluted bleach sitting for more than a few minutes.

Can you rinse coffee grounds down the sink?

It’s not a good idea to pour coffee grounds down the sink, even with water. Coffee grounds are one of the most common culprits of clogged drains.

‘They don’t dissolve in water, so they can clump together and form a hard, rock-like blockage in the drain,’ said Spencer.

 How to choose less polluting and more sustainable products and then dispose of them safely.

How to prevent drains from getting blocked

There are simple things you can do every day to help prevent drain blockages, including scraping plates before washing up, and brushing your hair before getting in the shower.

It's also worth occasionally using a little drain unblocking solution, even if your drain isn't blocked, to prevent blockages building up in the first place.

However, eco mode often uses cooler water to save energy. Spencer says the shorter or less intensive wash cycles may not effectively dissolve grease, oils, or food residues. If grease or fats aren't properly dissolved, they could accumulate in the dishwasher or drain pipes, contributing to blockages over time. Using a high-temperature or intensive cycle occasionally can help break down grease and food debris more thoroughly, which reduces the risk of build-up.

source https://www.which.co.uk/news/article/how-to-unblock-a-sink-a7aDE8S5nR3T