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How we test carpet cleaners

By Matt Stevens

The best carpet cleaners don't just leave your carpets clean, but looking like new. Read on to find out about how we test carpet cleaners.

Put us to the test

Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.

At Which? we go to great lengths to rigorously test carpet cleaners to help you avoid buying one of the really poor ones that fail to tackle grimy carpets. You can trust that any carpet cleaner we recommend really is the best for you and your home.

Our reviews answer the most crucial questions about carpet cleaners - a Best Buy will leave carpets refreshed and looking like new, but a Don't Buy will leave carpets dirty and looking tired. Spending a lot of money in the shops will not necessarily get you a good one. We've tested models that cost £300 but do a bad job of cleaning carpet.

Our independent tests look at more than just cleaning power, they answer all the most important carpet cleaning questions including:

  • How clean will it leave tired and grimy carpets?
  • What's the carpet cleaner like on dried-in stains?
  • How wet will the carpet cleaner leave my carpets?
  • Is the carpet cleaner quiet and easy to use?
  • Should I buy it?

Only the models that do brilliantly across all of our tests can join the ranks of our Best Buy carpet cleaners.

How clean does it leave tired, grimy carpets?

We test the cleaning power of each machine on three pieces of soiled carpet. Once the carpet has been cleaned and dried, we expertly assess the samples with a machine called a spectrometer (which measures brightness). Marks are also deducted for uneven results, such as stripes being left along the carpet.

As part of our carpet cleaning tests, we also measure how close to the edge of the room a carpet washer can clean. Some models can clean quite close to the edge, but some models we've tested leave a large margin of grubby uncleaned carpet around the edge of a room - more than 7cm in one case.

The picture (above) shows the difference between an uncleaned carpet on the left, a carpet cleaner that gets one star in our testing  in the middle - the carpets are still dirty - and a carpet cleaner that can deliver a five-star clean - the carpet is left clean and refreshed.

Skip straight to our carpet cleaner reviews to find out the top-scoring models we recommend.

What's the carpet cleaner like on dried-in stains?

While they're not designed for tackling tough stains, we check how well carpet washers cope with common spills.

Carpet samples are stained with 10ml of red wine, coffee and gravy and left to dry for 24 hours. The carpet is then cleaned according to the carpet cleaner manufacturer's instructions and assessed to see how much of the stain has been removed.

How wet will the carpet cleaner leave my carpets?

It's not just about the washing - a good carpet cleaner should not leave your floors waterlogged after the cleaning is done.

To check how wet carpets are left, we weigh carpet samples before cleaning is done and then again after one hour, five hours and 24 hours to see how much water they're still holding. The more stars a model gets in our drying test, the less amount of amount of water you can expect to find in your carpet.

How quiet and easy to use is the carpet cleaner?

When it comes to a carpet cleaner's features, we don't just take the manufacturer's word for it - we check the credentials of each machine on test.

We measure the length of the carpet cleaner's cord and nozzle, how much water the tank can hold without leaking and how much the machine weighs when the water tank is empty and full. Instructions are marked for their clarity and we see what the machine is like to use - how easy it is to assemble, fill and empty the water tank and push the cleaner around.

In use, we ask a panel of three experts to assess how noisy the carpet cleaner is - and whether the noise is particularly intrusive or irritating. Having an unbearably loud carpet cleaner could be the difference between a carpet cleaner you use frequently and one that lives in the cupboard until you can't ignore your dirty carpets any longer.

68%A carpet cleaner needs to score 68% to be a Which? Best Buy

Should I buy it?

Each of the assessments described above goes part way to making up a total test score, which is the percentage figure awarded to each carpet cleaner. But certain assessments are more important than others and so carry different weights:

  • 60% Carpet cleaning
  • 30% Ease of use
  • 10% Noise

A model needs to score 68% or more to be considered a Best Buy carpet cleaner, and those scoring below 40% are highlighted as Don't Buy carpet cleaners that are so bad we think you should avoid them altogether.

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