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1 September 2021

Best kitchen drain unblockers

Avoid a clogged drain and a sink full of dirty water with our top-rated picks to clear trapped food waste
Joey Willoughby-Rainsford

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 01 September 2021.

The best kitchen drain unblockers

Only logged-in Which? members can view the drain unblocker test results below. If you're not yet a member, you'll see an alphabetically ordered list of the kitchen drain unblockers we tested. Join Which? now to get instant access to our test results and Best Buy recommendations below. 

Buster Kitchen Plughole Unblocker

Buster Kitchen Plughole Unblocker

Cheapest price: £2.30 available at Amazon, Waitrose. Also available at Asda, Homebase, Morrisons, Ocado, Robert Dyas, Sainsbury's

Size: 200g

Suitable for a septic tank: Yes

Buster claims its Kitchen Plughole Unblocker 'blasts' through fat and food trapped in drain and pipes. 

Remove as much water from the drain as possible before pouring the entire contents slowly down the plughole avoiding spillage on the sink's surface. 

Leave it to work for a maximum of 20 minutes, then flush through with lots of hot water. 

What did we think of Buster Kitchen Plughole Unblocker? Log in now or join Which? to see our full test results.

Cillit Bang Drain Odour Eliminator & Unblocker Gel

Cillit Bang Drain Odour Eliminator & Unblocker Gel

Cheapest price: £2 available at Wilko. Also available at Asda, Amazon, 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. 

Cillit Bang says its 'powerful formula' unblocks tough clogs while it cleans and kills odour-causing bacteria.

To use, pour 500ml of gel into the drain, leave it for 30 minutes, then flush with hot water

Was it 'bang and the dirt is gone'? To find out, log in to your account or join Which? to see our full test results.

Domestos 15 Minute Sink & Pipe Unblocker Gel

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

Domestos boasts that its unblocker gel needs only 15 minutes to 'eliminate' bathroom and kitchen blockages.

Simply pour the entire bottle into the drain and allow 15 minutes for it to work. 

Afterwards, flush through the pipes with hot water.

Was 15 minutes all it took to clear our drain? Find out by logging in or joining Which? to see the test results.

Ecozone Kitchen Drain Unblocker

Ecozone Kitchen Drain Unblocker

Cheapest price: £5.59 available at Ocado. Also available at Amazon, Robert Dyas

Size: 1 litre

Suitable for a septic tank: Yes

Ecozone says its Kitchen Drain Unblocker is cruelty-free and vegan. 

Shake the bottle well, then pour half the contents down the plughole. 

Leave the solution to work for 12 to 24 hours, then flush with two litres of warm water.

Were the results of this product worth a 12-hour wait? Log in or join Which? to find out. 

HG Kitchen Drain Unblocker

Cheapest price: £4 available at Tesco. Also available at Amazon, B&Q, Robert Dyas

Size: 1 litre

Suitable for a septic tank: Yes

According to HG, its Kitchen Drain Unblocker has been specially developed to clear blockages caused by 'very stubborn' food residue and fat.

Remove as much water from the sink as you can before pouring 300ml down the drain. 

Then pour the same quantity of lukewarm water and leave for a minimum of six hours. 

Finally, rinse the drain through with water.

How did we find HG Kitchen Drain Unblocker? Find out by logging in or joining Which? to see our full test results.

Mr Muscle Power Gel Drain Unblocker

Mr Muscle Power Gel Drain Unblocker

Cheapest price: £2.60 available at Waitrose. Also available at Asda, Amazon, Ocado, Sainsbury's, Tesco, Wilko

Size: 500ml, also comes in 1 litre

Suitable for a septic tank: Yes

Mr Muscle claims its power gel can 'destroy the worst clogs'. 

If you have a blockage, pour 500ml down the drain and wait five minutes. 

Then flush the drain through with hot water.

Did this product really only need five minutes? Log in or join Which? to find out. 

Ocado Sink & Drain Unblocker Gel

Ocado Sink & Drain Unblocker Gel

Cheapest price: £2 available at Ocado

Size: 500ml

Suitable for a septic tank: Yes

One of the cheaper options in our selection.

To use, pour the entire contents down the plughole and leave for three hours. 

Once complete, flush the pipes with hot water.

What did we think of this drain unblocker gel? Log in or join Which? to see the full results of our tests.

Sainsbury's Sink & Plughole Unblocker

Sainsbury's Sink & Plughole Unblocker

Cheapest price: £2.25 available at Sainsbury's

Size: 500ml

Suitable for a septic tank: Yes

Sainsbury's says its sink unblocker delivers immediate action. 

Pour the whole bottle down the drain. 

Leave for 15 minutes, then rinse through with hot water.

How effective was this product? Find out by logging in or joining Which? to see our full test results.

Dri Pak Soda Crystals

Soda Crystals

Cheapest price: 79p available at Ocado. Also available at Tesco

Size: 1kg

Suitable for a septic tank: Yes

Soda Crystals are a product with a lot of cleaning utility, from cleaning your clothes to your washing machine. 

To clear a drain, mix 200g of Soda Crystals in 500ml of hot water. 

Then pour down the drain and leave for 30 minutes. 

Afterwards, flush through with hot water. 

It's the cheapest product in our selection, but how did it compare with the others? Log in or join Which? to find out.

Tesco Sink & Drain Unblocker

Tesco Sink & Drain Unblocker

Cheapest price: £2 available at Tesco

Size 500ml

Suitable for a septic tank: Waiting for a response from the manufacturer

Tesco says its Sink & Drain Unblocker has a powerful, fast-acting formula that eliminates bad odours.

To use, pour the entire contents down the plughole. 

Wait 15 minutes, then rinse through with hot water.

Did this product live up to Tesco's claims? Log in or join Which? to find out.

Essential Waitrose & Partners Drain Unblocker

Essential Waitrose & Partners Drain Unblocker

Cheapest price: £2.25 available at Waitrose

Size 500ml

Suitable for a septic tank: No

Waitrose & Partners claims this product 'gets to work immediately and dissolves build up'. 

When using, pour the whole bottle of liquid down the drain. 

Leave for 15 minutes, then flush hot water through the pipes.

How well did this drain unblocker do in our tests? Find out by logging in or joining Which? to see our full test results.

Drain unblocker home remedy: bicarbonate soda, salt and vinegar

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: 

  • Scrape plates Make sure you remove food residue from your plates, bowls and utensils before you put them in the sink.
  • Drain protector Get a drain protector to catch stray bits of food residue before they disappear down the plughole.
  • Enzyme cleaning sticks Dropping an enzyme cleaning stick down the plughole once a month is a good way to prevent germs, odours and blockages. 
  • No coffee grounds in the sink Throw away your coffee grounds in your food waste, compost or bin.
  • Collect the fat Collect fat and grease from cooking in a disposable container (juice or milk carton or another non-recyclable container) before putting it in with your general waste.

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. 

Explosive (symbol: exploding bomb)
Explosive (symbol: exploding bomb)
A substance that under defined test conditions when dry or under the effect of flame or heat may explode.
  • Read and use instructions for the given material.
  • Ensure containers are stored in a cool, well-ventilated place with tight-fitting lids.
  • Store away from sources of heat and ignition. 
  • Ensure the material and its containers are disposed of in a safe manner.

Flammable (symbol: flame)

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. 
  • Avoid ignition sources (sparks, flames and heat). 
  • Keep your distance. 
  • Wear protective clothing.
Oxidising (symbol: flame over circle)
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.
  • Read and use instructions for the given material. 
  • Ensure containers are stored in a cool, well-ventilated place with tight-fitting lids. 
  • Store away from sources of heat and ignition. 
  • Ensure the material and its container are disposed of in a safe manner.
Corrosive (symbol: corrosion)

Corrosive (symbol: corrosion)
May cause burns or destruction of living tissue on contact with skin.
  • Wear suitable protective equipment (PPE).
  • Remove and dispose safely of any contaminated clothing.
  • In the event of contact with skin, wash immediately with plenty of water. 
  • In the event of contact with the eyes, rinse immediately with plenty of water for 15 minutes and seek immediate medical help. 
Acute toxicity (symbol: skull and crossbones)

Acute toxicity (symbol: skull and crossbones)
May cause a severe health risk or even death if ingested, inhaled or penetration of the skin occurs even in low volumes or quantities.
  • Wear suitable protective equipment (PPE). 
  • In the event of contact with skin, wash immediately with plenty of water. 
  • In the event of contact with the eyes, rinse immediately with plenty of water for 15 minutes and seek medical advice. 
Hazardous to the environment (symbol: environment)

Hazardous to the environment (symbol: environment)
Presents or may present a danger to one or more parts of the environment. These substances are usually very toxic to aquatic organisms.
  • Ensure containers are stored in a cool, well-ventilated place with tight-fitting lids.
  • Take measures to safeguard against accidental spillage.
  • Ensure the material and its containers are disposed of in a safe manner.
Health hazard/Hazardous to the ozone layer (symbol: exclamation mark)

Health hazard/Hazardous to the ozone layer (symbol: exclamation mark)
May cause irritation (redness or rash) or less serious toxicity. May damage the ozone layer. 
  • Keep away from skin and eyes. 
  • Avoid release to the environment.
Serious health hazard (symbol: health hazard)

Serious health hazard (symbol: health hazard)
May cause serious and prolonged health effects on short or long term exposure.
  • Do not swallow the material, allow it to come into contact with skin or breath it in.
Gas under pressure (symbol: gas cylinder)

Gas under pressure (symbol: gas cylinder)
Contains gas under pressure. Gas released may be very cold. The gas container may explode if heated. 
  • Do not heat containers. 
  • Avoid contact with skin and eyes.

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. 

MCALPINE ADJUSTABLE INLET TUBULAR 'P' TRAP WHITE 40MM

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 products 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 Fellie Kitchen Sink Stainless Steel Sink Catering Single Sink

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 product had worked.

Each product was tested twice. 

How we choose these kitchen drain unblockers

We selected one product per brand, looking at liquid or pouring products available in national retailers. 

We purchased all the products we tested