Do Water Filters Remove Limescale?

Limescale is a hard chalky substance that is left on appliances when hard water evaporates. It is made of calcium, magnesium, and carbonate ions in hard water. Limescale contributes to the deterioration of appliances and so it’s a good idea to get rid of it before it causes problems.

Where does limescale come from?

Limescale is formed when water containing dissolved calcium bicarbonate (temporary hard water) is heated and evaporates, leaving behind insoluble calcium carbonate. Boiling permanent hard water does not result in scale formation since calcium sulfate, which causes permanent hardness, does not decompose when heated. Scales also form when calcium and magnesium ions in water react with compounds found in soaps to form insoluble scum.

The undesirability of limescale comes from aesthetic, efficiency, and cost considerations. When it forms on surfaces it makes them look dirty and ugly. Scale formation also clogs water pipes thereby reducing rates of flow. It also reduces the capacity to transfer heat in appliances like kettles, coffee machines, washing machines, and boilers which leads to high energy use and increased costs of maintenance. Additionally, it introduces stress on joints which can cause damage.

Despite its bad effects, limescale which is simply calcium carbonate has been used for centuries in construction as the starting ingredient for building lime and manufacture of classroom chalk. In addition to that, it is a major ingredient in making paints, ceramics, kids’ nappies, adhesives, fillers, and stained glass windows when mixed with putty. Limescale generally poses little or no danger to human health as its presence in water has been linked to the formation of strong bones and teeth, apart from being a strong antacid and a rich source of calcium.

Is limescale the same as calcium?

No. Limescale is the common name for the water-insoluble, white and chalky substance which normally appears as deposits in kettles, washing machines, boilers, and water pipes. It is composed mainly of calcium carbonate (lime), magnesium carbonate, manganese carbonate, and traces of iron-containing compounds which may add a reddish-brown color to it when present. On the contrary, calcium is a reactive metallic element that occurs naturally in rocks in combination with non-metal ions such as carbonates, sulfates, silicates, nitrates, and chlorides, among others.

What removes limescale from water?

The most common way of removing limescale from water is ion exchange (IX), which uses resins rich in negative ions to trade calcium and magnesium ions in hard water with sodium, thus eliminating scale. The choice of ion exchange resins to use should be made after testing the water to know what needs to be removed or reduced.

Because it works based on the principle of selective removal according to the ionic strength of the charged ions in water and the resin, no particular resin is specific for a given ion. Ion exchange processes are also mostly reversible hence the exchange resins can be renewed and used again.

A typical IX system consists of a pressure tank containing sulfonated polystyrene beads that can replace hard ions with soft ions like sodium. A tank filled with concentrated sodium chloride (brine) is then connected to regenerate the resin at regular intervals when it gets saturated.

Nanofiltration (NF) and reverse osmosis (RO) are also viable methods for removing limescale and some filter brands normally use them in addition to IX. NF uses nano filters with pores smaller than one nanometer to block scale-causing ions which are large in diameter and cannot pass through them.

It operates at lower pressures than RO, uses less water, and may be used for selective removal of ions that cause scaling (membrane softening). In RO, pressure greater than the normal osmotic pressure and an ultra-thin membrane is used to force water molecules from their region of high concentration to their region of low concentration, across a semi-permeable membrane, leaving behind the scale minerals. 

Do Brita filters filter out lime?

Yes, some Brita water filters contain ion exchange resin which removes calcium and magnesium ions thereby eliminating limescale. They are NSF-certified products that have been tested to meet the NSF/ANSI 53 sanitation and efficacy standards. Many household water treatment systems like entire house systems, under-sink filters, and refrigerator filters also contain reverse osmosis and distillation units. These may be much more expensive and complex but are the most effective at removing limescale 

Does coke get rid of limescale?

Coke contains low concentrations of citric and phosphoric acids which lowers its pH level thus it can react with limescale. It also contains carbonic acid formed when carbon dioxide used for making it fizzy dissolves in water. Being weakly acidic, a relatively long duration is needed for the soda to be in contact with limescale to dissolve it. Coke is a more cost-effective method of removing limescale as opposed to other liquids like vinegar and hydrochloric acid.

How do you get rid of heavy limescale?

When limescale deposits have grown on a surface for a long time, filtration becomes out of the question as filters only remove limescale while still in the water. To remove this type of scale, acids are usually used to react with the limescale and form soluble salts which can then be washed away with water. Strong acids like hydrochloric acid are recommended for heavy scale formed in hard-to-reach areas like inside toilet bowls, while open areas and appliances can be descaled using weakly acidic solutions vinegar (acetic acid), citric acid, lactic acid, formic acid, or even coke.


To sum it all up, water filtration systems have been hailed as the green choice and the go-to method for removing limescale and other contaminants from the water. Techniques, like scraping, hydro-blasting, and the use of aggressive chemicals have been found to shorten the life of pipes and machinery. It is not advisable to ignore limescale until it becomes problematic and therefore, the only sure way of preventing its formation is by using water filtration. You should consider investing in one that incorporates at least two or three filtration stages for maximum protection. Here is a good buying guide that explains the different options you have.