We put 11 kitchen drain unblockers from popular brands including Cillit Bang, Domestos and Mr Muscle to the test in May 2021, on a U-bend blocked up tight with stubborn food residue and grease.
We also tested the home remedy of bicarbonate soda, salt and vinegar to see how it compared.
The products below are suitable for food blockages. If you want to unblock a drain clogged with hair, take a look at our guide to the best shower drain unblockers.
As with any bleach-based products, make sure you always wear gloves, old clothes and follow the instructions carefully.
Pricing and availability last checked 7 March 2022.
The best kitchen drain unblockers from our test
Best Buy: Mr Muscle Power Gel Drain Unblocker
Cheapest price: £2.75 available at Ocado, Waitrose, also available at Amazon, Asda, Ocado, Tesco, Sainsbury's, Wilko.
Size: 500ml, also comes in 1 litre
Suitable for a septic tank: Yes
Pros: Clears the pipes, works within five minutes
Cons: In the smaller size it's a single-use plastic bottle
Our verdict: We found Mr Muscle Power Gel to be simple to use, effective and the fastest acting of all those we tested.
All the drain unblockers tested worked (although, some needed a bit of extra help as we explain), but Mr Muscle Power Gel was easily the fastest.
Within five minutes the clogs in our drains were dissolved.
If getting the job done fast is what's important to you, then have a bottle of this waiting under your sink.
It was also a Best Buy in our shower drain unblocker tests, so we feel this is a very useful product to have at home.
How the rest of the kitchen drain unblockers fare
Here's our verdict on the other kitchen drain unblockers we tested, listed alphabetically.
Buster Kitchen Plughole Unblocker
Cheapest price: £2.50 available at Amazon, Ocado, also available at Robert Dyas, Homebase, Morrisons, Waitrose.
Size: 200g
Suitable for a septic tank: Yes
Pros: Doesn't leave a lingering scent
Cons: We needed a plunger to completely remove the blockage, single-use plastic bottle
Our verdict: This product did remove the clog, but the mass of the granules created a new blockage we had to force out with a plunger.
In both of our tests, Buster Kitchen Plughole Unblocker dissolved the clogs into a greasy acidic sludge, but the weight and mass of leftover granules fused together to form a new blockage.
However, this second clog was easily flushed away with a single strike of our plunger.
When you use this product don't leave it in the pipes for more than 20 minutes, make sure you wear gloves, don't get any on your skin and open all the windows in the room.
Cillit Bang Drain Odour Eliminator & Unblocker Gel
Cheapest price: £2.25 available at Wilko, also available at Amazon, Asda, Ocado.
Size: 500ml
Suitable for a septic tank: The manufacturer says they are unable to test on all septic tanks. Therefore, it's safest for you to check with your septic tank provider.
Pros: Clears the pipes
Cons: Single-use bottle
Our verdict: An affordable product that cleared our U-bend of grease and food residue.
This unblocker gel from Cilit Bang was not the fastest, but it was by no means the slowest product from our investigation.
It effectively removed the clogs in both of our tests.
Domestos 15 Minute Sink & Pipe Unblocker Gel
Cheapest price: £3 available at Ocado, also available at Asda, Wilko.
Size: 500ml
Suitable for a septic tank: Yes
Pros: Clears the pipes, works within 15 minutes
Cons: Single-use bottle, very small printed instructions on bottle
Our verdict: A fast-acting unblocker that cleared the pipes of our clog.
You won't be disappointed with this if you need to unblock your sink.
Although the printed instructions are very small, it's an easy to use product.
Ecozone Kitchen Drain Unblocker
Cheapest price: £5.99 available at Ecozone Direct, also available at Ocado.
Size: 1 litre
Suitable for a septic tank: Yes
Pros: Clears the pipes, doesn't have too strong a scent
Cons: Can take up to 12 hours to work, no child safety cap (although it's not required by law to have one)
Our verdict: It does work, but 12 hours is a long wait.
During our tests, the Ecozone Kitchen Drain Unblocker did work to remove the clog from our pipes but it took a very long time.
For most people, this won't be an issue if you make sure you do it in the evening before you go to bed.
HG Kitchen Drain Unblocker
Cheapest price: £4.25 available at Tesco, also available at Amazon, B&Q, Robert Dyas.
Size: 1 litre
Suitable for a septic tank: Yes
Pros: Clears the pipes
Cons: Can take up to six hours to work, no child safety cap (although it's not required by law to have one)
Our verdict: Slower than many of the others, but still as effective.
You get more for your money, but this product isn't as simple as just pouring and leaving as you need to mix it with water.
It does take a minimum of six hours to work, but if you're happy to wait or leave overnight, this could be the one for you.
Ocado Sink & Drain Unblocker Gel
Only available at Ocado: £2.25.
Size: 500ml
Suitable for a septic tank: Yes
Pros: Clears the pipes
Cons: Can take up to three hours to work, single-use plastic bottle
Our verdict: Not the fastest, but by no means less effective.
Although it took three hours both times we tested it, this Ocado Sink & Drain Unblocker Gel proved just as effective as most of the others from our test.
Sainsbury's Sink & Plughole Unblocker
Only available at Sainsbury's: £2.25.
Size: 500ml
Suitable for a septic tank: Yes
Pros: Clears the pipes, works within 15 minutes
Cons: Single-use bottle
Our verdict: Good results with a quick turnaround.
It only took 15 minutes for this plughole unblocker from Sainsbury's to cut through the grease and food residue.
Once it had finished, the pipes and U-bend were squeaky clean.
Soda Crystals
Cheapest price: 80p available at Ocado, also available at Morrisons.
Size: 1kg
Suitable for a septic tank: Yes
Pros: Clears the pipes, offers lots of cleaning options
Cons: Requires more preparation than the others
Our verdict: Soda Crystals worked, but it's a faff to get ready, especially compared with the other products we tested.
You need to prepare the solution first, then pour it down the drain. On both occasions when we tested it, the blockage was removed within 30 minutes.
Soda Crystals is an incredibly affordable product with a lot of cleaning utility as you can use it to clean your washing machine, barbeque, pots and pans, as well as stain removal on clothes and fabrics.
Tesco Sink & Drain Unblocker
Only available at Tesco: £2.
Size: 500ml
Suitable for a septic tank: Waiting for a response from the manufacturer
Pros: Clears the pipes, works within 15 minutes
Cons: Single-use plastic bottle
Our verdict: A speedy solution to a blocked drain.
After 15 minutes, the Tesco Sink & Drain Unblocker had done its job and removed the clog from our U-bend.
Essential Waitrose & Partners Drain Unblocker
Only available at Waitrose: £2.25.
Size: 500ml
Suitable for a septic tank: No
Pros: Clears the pipes, works within 15 minutes
Cons: Single-use plastic bottle
Our verdict: A fast-acting unblocker with consistent results.
Like many of the other bleach-based products, this unblocker from Waitrose & Partners worked quickly to get rid of the clog.
Drain unblocker home remedy: bicarbonate soda, salt and vinegar
Did this home remedy get rid of the greasy food residue clogs in our tests? In short, no.
In both attempts, the mixture of bicarbonate soda (125g), salt (125g) and vinegar (125ml) seemed to do nothing but fizz and spit in the plughole.
After waiting 10 minutes, the clog was still firmly in place and so a lot of rigorous plunging action was required to dislodge it.
However, this home remedy is good for regular drain maintenance to prevent major blockages.
How to prevent kitchen drain blockages
Most of the time serious blockages in drains are preventable. Here are some simple steps to help prevent a dreaded blocked sink:
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What are the chemical hazard symbols and what do they mean?
Many drain unblockers contain chemicals that are hazardous to us and the environment.
Below you can see the symbols found on some products, what they mean and the safety advice for handling them.
| Chemical hazard symbols and what they mean | |
| Explosive (symbol: exploding bomb) | |
| A substance that under defined test conditions when dry or under the effect of flame or heat may explode. | |
| Flammable (symbol: flame) | |
| Flammable if exposed to ignition sources, sparks or heat. Some substances with this symbol may give off flammable gases in contact with water. | |
| Oxidising (symbol: flame over circle) | |
| May cause explosion, fire or damage to living tissue resulting in chemical burns. Reacts with other substances to produce a highly exothermic reaction. | |
| Corrosive (symbol: corrosion) |
How we tested kitchen drain unblockers
To find out which of our selected drain unblockers was the best, we put the whole selection through the following test.
The setup
Using a freestanding catering sink, we got one 44mm U-bend per test and stuffed it with a clog made from equal parts grated broccoli, melted lard and breadcrumbs, which we then allowed to harden for 12 hours.
To ensure each clog was firmly lodged in place, 500ml of boiling water was poured into the plughole before the tests began.
The unblockers were then applied following their instructions and left for the minimum required time.
Afterwards, the U-bends were flushed through with eight litres of hot tap water.
If necessary, a plunger was used at this point. We've noted above when a plunger was needed.
The test
The pipes were examined with a tube camera before and after the products were applied to see how effectively they worked.
Then we timed how long it took for eight litres of cold tap water to pass through the U-bend and pipes.
We compared these timings to a test done on an unused U-bend. The quicker the water passed through the better, the unblocker had worked.
Each product was tested twice.
How we choose these kitchen drain unblockers
We selected one drain unblocker per brand, looking at liquid or pouring products available in national retailers.
We purchased all the products we tested.