How we test limescale remover
By Patrick Gallagher
Find out how our tests reveal which limescale removers are best at shifting unsightly scale build-up.
We rigorously test each limescale remover spray we review in exactly the same way, so you can be confident that only those that remove limescale and soap scum effectively earn our Best Buy recommendation.
Below, we explain how we test limescale remover sprays, the difference a Best Buy will make to your efforts to restore sparkle to your bathroom surfaces, and how our reviews help you avoid the sprays that neither shift limescale nor stop soap scum in its tracks.
Our reviews answer the most crucial questions about limescale removers, including:
- How well does it shift limescale?
- How well does it clean off soap scum?
- Could it damage my surfaces?
- Should I buy it?
Only the ones that excel in all these areas can be Best Buy limescale removers.
How well does the limescale remover shift limescale?
This is the key part of our test, and we found some products are significantly better than others – the best limescale removers we tested shift four times more scale than the worst.
To see how well each spray removes limescale, we immerse a slab of a specially chosen type of rock (which has the same properties as limescale) in them for the time stated on the bottle. We weigh the slab before and after to assess how much limescale has been removed. We do it like this as it's the most reliable and consistent way of assessing how much limescale each spray can remove.
Products that remove the most limescale in the stated action time are the most powerful, and therefore the most effective if you have hard water at home. They should also reduce how frequently you need to clean limescale from your bathroom or kitchen surfaces by removing it more effectively each time you clean. And you're likely to need to use less of them to get a good result, so they could save you money in the long run, too.
To give each product the best chance of success, we follow the maximum action time written on the bottle. For some products this is up to five minutes.
See which products best tackle limescale in our full limescale remover reviews.
How well does the limescale remover clean off soap scum?
If you have hard water, you may notice a build-up of stubborn dirt and grime around your bathtub or shower. This is soap scum, created from a combination of soap, dirt and hard water.
To test how well each limescale remover can clean off this unsightly tide mark, we dye it bright blue and cover white tiles in it so we can clearly see how much soap scum is removed and how much left behind. Because soap scum doesn’t conveniently collect only on flat surfaces, we place one tile horizontally and one vertically before applying the cleaner to them. The best cleaners leave the white tiles shiny and pristine; the worst leave blue streaks or rough residue.
Only two products on test earned the full five stars for soap-scum removal. Find out which in our full limescale remover reviews.
Could it damage my surfaces?
We introduced a test of how aggressive limescale removers are on surfaces after 11% of Which? members told us they’d noticed damage to a surface after using one.
We put each limescale remover on 10 common kitchen and bathroom materials – including grout, ceramic, and stainless steel – and checked them after eight and 24 hours for any damage or discolouration. All cleaners state that you should rinse them off after use, so our test checks what would happen if you missed rinsing off a spot.
Should I buy it?
The assessments described all contribute to the overall test score we give each limescale remover. The higher the score, the better the product did in our tests.
Some elements of the test are more important than others, and so carry different weightings. We think a bathroom limescale remover’s most important job is to shift limescale from surfaces, so the highest proportion of our total test score is based on this. Our overall ratings ignore price and are based on:
- 50% Limescale removal
- 30% Soap-scum removal
- 20% Surface care
A limescale remover needs to earn 70% in our rigorous tests to become a Best Buy. Those scoring less than 45% become Don’t Buys.