Long Island plumbing here are 10 Ways to Remove Limescale. Limescale forms when hard water is heated above 61°C or when it is left to evaporate on surfaces such as taps and showerheads. Hard water is water that contains high quantities of calcium and magnesium ions. These hardness minerals, in the form of calcium carbonate and magnesium carbonate, are what precipitate out of hard water to form limescale. Therefore, to clean or remove limescale, we need something that will dissolve or soften calcium carbonate and/or magnesium carbonate.
Acids are generally very good at dissolving things and in particular, the following list of acids will dissolve limescale.
Warning: Some of these acids are extremely hazardous and their use as a descaler is best left to professionals. Additionally, some acids, hydrochloric acid in particular, will discolour (blacken) chrome taps and fittings.
1) Acetic acid
Vinegar is just dilute acetic acid, so it's readily available around the home.
Mix half a cup of water and half a cup of white vinegar (not malt vinegar) to remove limescale from an electric kettle. Bring the mixture to the boil and leave overnight. Rinse out the next day.
Clean shower heads by soaking overnight in a tub of undiluted white vinegar. Mix with borax (50:50) to make your own, cheap, limescale cleaner for taps, tiles, baths and basins.
2) Citric acid
Citric acid is present to some degree in all citrus fruits, but lemons generally have the highest concentration. Lemon juice generally works better than vinegar and leaves a more pleasant smell.
To clean dishwashers and washing machines, use one cup of lemon juice instead of the normal detergent. Run a normal wash cycle without clothes / dishes. For washing machines, put the lemon juice in the soap powder dispenser. For dishwashers, just pour it straight into the bottom of the machine.
To clean electric kettles, follow the instructions for vinegar but replace the vinegar with lemon juice. Same for shower heads.
When cleaning taps, the problem comes when trying to keep the lemon juice in contact with the limescale long enough for it to dissolve or soften. One way to overcome this problem is to soak a cloth in lemon juice, wrap it around the tap and leave overnight.
Citric acid is also the main constituent of Limelite sprays, gels, descalers and wipes.
3) Formic acid
Formic acid, produced naturally by ants and contained in bee stings, will dissolve limescale. It can be bought as Kilrock K or in dilute form as Techno Swan. It is also one of two acids used in Cillit Bang Grime and Lime (the other being sulphamic acid).
4) Glycolic acid
Although mainly used in cosmetics, glycolic acid is as a minor ingredient in a number of commercial limescale cleaning products, including R8 Kettle Descaler. DuPont market glycolic acid for removing hard water scale deposits in industrial water and boiler systems.
5) Hydrochloric acid
Sold in Spain as agua fuerte (strong water). Be warned, hydrochloric acid is a strong acid and will burn skin - read all safety data thoroughly. It fizzes on contact with limescale and the vapour it gives off (hydrogen chloride) is toxic, so probably best to leave this one for the experts.
If you still want to try it, then a safer alternative, which contains hydrochloric acid as the main active ingredient, is No Nonsense Path Patio & Driveway Cleaner. Other kitchen and bathroom cleaners that contain hydrochloric acid are Harpic duraguard limescale remover and Lifeguard limescale remover.
6) Lactic acid
Sometimes known as milk acid, lactic acid is also a good limescale remover. Lactic acid forms when lactose, which is found in milk, is broken down by bacteria and is therefore found in sour milk. However, we do not recommend trying to remove limescale with sour milk. Instead, buy some Oust. Oust All Purpose Descaler contains 30 to 50 percent lactic acid and can be used for cleaning kettles, coffee maker and irons.
7) Oxalic acid
Oxalic acid is 3,000 times stronger than acetic acid and mainly used as a bleaching agent or to remove rust. It will remove limescale, but is rarely used in domestic cleaning products. It is used in Oxal Wash to remove limescale (among other things) from train exteriors.
8) Phosphoric acid
The principal use of phosphoric acid is as a rust remover, but it is also used in many commercial limescale cleaners and is found in some soft drinks, notably cola.
In the film, Limescale, the main character stops drinking water and only drinks cola in the belief that limescale is building up in his body and cola will dissolve the hardened deposits. Urban Myth according to the film synopsis, but both main brands of cola contain phosphoric acid (E338).
Phosphoric acid is sold in it's raw state as a descaler on eBay and used in many commercial limescale cleaners. Proprietary cleaners that contain phosphoric acid include HG Professional Limescale Remover or Hagesan Blue.
9) Sulphamic acid
Sulphamic acid is widely used in commercial limescale cleaning products and is a less hazardous alternative to hydrochloric acid. For professional use, it is an active ingredient of Fernox DS3 limescale remover and in the home it is one of the constituents of Cillit Bang Grime and Lime.
10) Sulphuric acid
Knock Out Drain Cleaner is almost pure sulphuric acid but is not marketed as a limescale cleaner (although it will do the job). Sulphuric acid extremely hazardous and best left to the experts. Even then, few, if any, limescale removal products on the market contain sulphuric acid. Avoid!