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.
With help from Spencer Darley of Which? Trusted Trader company Drain Jet Yorkshire, we’ll walk you through the best methods to unblock your kitchen sink or bathroom drains and reveal what you should never pour down your drain.
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What are the signs your sink is blocked?
Spencer said there are three key signs your drain might be getting clogged:
- SmellsIn the early stages of a drain blockage, you might notice unpleasant odours resembling rotten food, stale or musty smells or sewage-like odours. These smells occur because trapped debris begins to decompose or stagnant water allows bacteria to grow.
- A glugging soundA glugging sound from your drain usually indicates air is trapped in the pipes and struggling to escape as water flows past. ‘The glugging is the sound of the airflow getting more and more restricted,’ Spencer said.
- The water drains more slowlyIf the issue is not tackled, water may eventually stop flowing altogether.
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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: Often, a few firm plunges are enough to dislodge minor blockages caused by food particles or grease. Make sure there’s enough water in the sink to cover the plunger’s cup and create a tight seal before plunging vigorously.
- Try adrain unblocker: If plunging doesn’t do the trick, the next step is to use a drain unblocker. This can help break down stubborn grease, oil or soap build-up. Always follow the instructions on the product and take care when handling chemical unblockers.
- If the sink is still blocked, the issue may be trapped debris in the U-bend pipe. This means you will need to unscrew the trap–or U-bend– carefully.
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.
If you're struggling to reattach the U-bend, a small amount of washing-up liquid around the edges can help create a better seal and make it easier to tighten the connection. Just be sure not to overdo it, as too much could cause slipping or leakage.
Our independent testing has uncovered the best kitchen drain unblockers to help you pick the most effective one for your sink. Our Best Buy got the job done within five minutes.
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.
Keep your appliances running smoothly with our 9 maintenance tips to keep your kitchen looking good.
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 throughWhich? Trusted Traders, 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.
Unlike in kitchen sinks, the U-bend under a bathroom drain may be harder to access, as it is often concealed within the floor, walls or behind panels. Just like in the kitchen, a plunger is the first go-to. If that doesn't work, fear not – our testing has revealed some of the best shower drain unblockers. For bathroom drains, unblockers designed to dissolve hair and soap scum are particularly effective. In fact, one of our Best Buys shrank down two large hairballs within 15 minutes.
- 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? Seehow to clean a shower screenandhow to descale a shower headto 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:
- PlungerKeep two plungers to hand at home – one for your sinks and one for your toilet. When using, ensure the rubber forms a seal over the drain, pump it up and down vigorously, then quickly release to see if the water drains. If not, try repeating a few times.
- Drain unblocker When we test drain unblockers, we try to replicate real-life scenarios as closely as possible, such as using hair mixed with shampoo for shower unblockers, and hair mixed with breadcrumbs for kitchen drain unblockers. The best ones clear pipes quickly by flushing out hair and debris, some in as little as five minutes.
- Drain protectorsThese are covers designed to stop debris and scraps from entering drains, while allowing water to flow through.
- Enzyme cleaning sticksThese are made of natural enzymes designed to digest fat, grease and soapy residue. In most cases, they're remarkably effective at keeping your drains clear and odour free. You simply drop one stick into the plughole once a month and then leave it to do its work in your U-bend.
- A hair snare or drain snakeSpencer said these can be 'a handy way to get hair out of bathroom drains'. In our testing, we pitted a Drain Millipede against a variety of shower drain unblockers; head to our guide to find out how it fared.
6 ways you might be polluting water without realising: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.
Spring cleaning tips: 7 ways to whizz through the big clean
Can you pour oil down the sink?
The main causes of blocked drains are known as FOG, which stands for Fats, Oils, and Grease. These substances are common culprits of drain blockages and can cause significant issues in plumbing systems when they accumulate. Water companies clear millions of litres of FOG from sewers every year.
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.
- Use kitchen roll to soak up grease from plates and pans before washing up. The best kitchen roll we tested had large, tough sheets that absorbed lots of liquid.
- 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.
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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.
With help from the chair of the British Cleaning Council, we tell you how to clean your toilet properly
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.
Instead, dispose of them in your bin, or you can compost them. If you don't know how, see our guide on how to make compost for our expert tips.
How to buy water friendly products: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.
Maintaining your plugs and pipes properly is key to making sure they don't get bunged up. Add a Best Buy cleaning spray and an spare toothbrush that you no longer use to your cleaning kit and make sure to give plugholes a scrub the next time you're polishing up your home. Spencer also recommends giving the trap underneath the sink a good clean every few months.
Severn Trent advises homeowners to flush only the 3 Ps - pee, poo and (toilet) paper – and keep a bin in your bathroom for all unflushable items, such as sanitary towels, tampons, nappies and wipes.
You may also want to vary the settings you use on your dishwasher. Using eco mode on your dishwasher is a great choice for reducing energy consumption and being more environmentally friendly.
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.
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