A limescale inhibitor is a water treatment solution that prevents limescale from forming in your pipes, washing machines, boilers, and other home appliances.

Limescale is a deposit or residue of hard water and appears as an off-white, chalk-like substance on most surfaces that hard water touches.

In the UK, as many as 13 million households are affected by the numerous consequences of limescale deposits – clogging, energy and detergent inefficiencies, frequent breakdowns, changes in water pressure, etc.

Fortunately, there are ways to deal with water hardness, and one simple way is to use a limescale inhibitor. 


What Causes Limescale?

Limescale is caused by high concentrations of minerals in water, with calcium and magnesium being the primary culprits. When water evaporates, or heat is applied, various deposits of calcium carbonate, calcium sulphate or magnesium hydroxide are formed.

Unfortunately, limescale problems are related to the geology of the region you are living in. The types of rocks that water passes through as it accumulates in groundwater reserves will determine the type of water you are supplied with.

Rainwater is naturally soft, but as it touches or permeates the ground, the types of rocks it enters into contact with will end up altering its composition. For example, in areas with non-porous rock structure like granite, water does not permeate the rock and simply flows off to rivers and streams.

Porous rock structure like limestone is easily permeated by rainwater, collecting particles of calcium and magnesium, which determine the hardness of water.

Water hardness can be easily measured with a water test strip or more expensive equipment to determine the level of hardness expressed in ppm (parts per million). Soft water is usually below the 60 ppm threshold, while very hard water is water that measures above the 180 ppm threshold.


Why is Limescale a Problem?

The problems caused by limescale range from the superficial to major issues that interfere with the proper operation of your household appliances. When it comes to limescale related issues, the two most common problem areas in your home are the kitchen and the bathroom.

Scale deposits will often cover taps, tiles, dishes, pots and pans with a whitish layer that can be tough to remove. In coffee machines, dishwashers, washing machines, kettles and other appliances limescale can harden around components making them less efficient and causing breakdowns.

Limescale will also build up in pipes, showerheads, and on other sanitary ware causing blockage or restricting the flow of water. It is this damage that usually stays hidden from view causes the most alarm among homeowners.

These are the effects of hard water on appliances and hard surfaces, but hard water can just as easily affect your skin and hair, causing dryness or itchiness. Likewise, hard water reduces soap and detergent efficiency by forming soap scum.

Whenever confronted with these issues, homeowners will seek out various descaling products that deal with the symptoms (e.g. they remove limescale from surfaces), but don’t solve the issue on the long run.

Luckily, long-terms solutions do exist and, as with most ailments, it’s better to prevent limescale formation than deal with its consequences.

These scale build-up prevention units are often marketed under the wider umbrella of water softeners, but as we will discuss in this article, there is a significant difference between limescale inhibitors and water softeners.


Water Softeners vs Limescale Inhibiting Filters

Limescale treatment filters, also known as water conditioners, are often marketed as water softeners, but there is a significant distinction that must be made: water softeners eliminate water hardness, while scale treatment filters or inhibitors prevent limescale build-up without eliminating water hardness.

Eliminating water hardness involves a chemical process, which exchanges hardness minerals with sodium ions. Preventing mineral deposit build-ups involves a physical process, which alters the structure of hardness minerals thereby preventing them from precipitating and sticking to surfaces.

The downside of the chemical process is that it uses softening salt to aid the ion exchange process, which results in water that is high in sodium and not quite palatable to our taste buds. The upside, however, is that you can enjoy all the benefits of soft water (softer skin and hair, softer clothes, less detergent usage, better soap lathering, etc.).

The downside of the physical process is that despite the fact that hardness minerals can no longer build up on surfaces, water remains hard and certain disadvantages linked to hard water (dry skin and hair, detergent inefficiency, etc.) remain. Even so, some of the advantages of the physical process, like the fact that it doesn’t alter the taste of water, rank this method high in the preferences of homeowners.


The Benefits of Using Limescale Inhibiting Filters

Undoubtedly, water softeners are some of the most efficient solutions in hard water treatment, yet the benefits of scale inhibitors are significant too:

  • Preventing scale build-up can be achieved without adding anything to water that might alter its taste or adversely affect your health.

Softened water is high in sodium, which not only taste bad, but it’s potentially dangerous for those on a low-sodium diet. Softened water is designed to protect your pipes and heating appliances, but it’s not the best choice of drinking water.

If you’re planning on installing a whole house water softening system, make sure you use a sodium removal water filter for drinking water.

Water softening systems tend to cost more than other water hardness treatment solutions. While a water softener may need regular maintenance, a limescale filter only needs replacement at the end of its service life.

  • Limescale water filters don’t use electricity, water, or salt

Beyond the initial investment of a water softener, you also need to factor in electricity use (although there are non-electric water softeners too), salt and water usage during the regeneration process. Limescale water filters don’t need any of these, so they’re more economical even in terms of maintenance.

  • Naturally occurring essential minerals are not removed.

Because water conditioners don’t remove minerals like calcium or magnesium, you can continue to enjoy great-tasting, wholesome water without worrying about mineral deposits in your appliances.

Neither water softeners, nor water conditioners are capable of removing bacteria, viruses, heavy metals, chlorine, fluoride, VOCs, THMs, or other common water pollutants. If your tap water contains these contaminants, you should also look into a water filter system that can remove such contaminants.


Which Water Conditioner Should You Use?

If you’re looking for a whole house scale treatment solution, we recommend one of Watts’s OneFlow scale control systems. The cost of a Watts OneFlow scale control system is comparable with the cost of high-performance water softening systems, however, the OneFlow line comes with the following system economy related advantages:

  • OneFlow systems don’t use electricity;
  • No salt is necessary for the process of eliminating scale;
  • OneFlow systems don’t have a backwash system and don’t waste any water.

Other than these advantages, Watts OneFlow scale control systems not only eliminate scale from water, but also aid in the removal of existing scale.

The system uses a physical process to prevent scale transforming dissolved minerals into microscopic crystal particles that stay suspended in water and don’t attach to surfaces. The Watts scale control system does not add anything to your water and doesn’t remove healthy minerals.

If you want a coffee machine filter or a vending machine filter that offers water filtration and scale treatment via a single system, we recommend the FT-Line VE Water Filter System, which can be used both for at-home water treatment or as an inline system for commercial applications.

The FT-Line uses two filter cartridges — a 5 micron sediment filter and a granular activated carbon filter with silico-polyphosphates. The system removes sediments, chlorine, VOCs, treats taste and odour issues, and offers scale treatment as well, making it one of the top choices of the catering sector.

Other than replacing the filters every 6 months, no further maintenance is required. Both the initial costs and filter replacement costs are low.

A water filter that can remove contaminants and offer scale treatment at the same time is probably the easiest and most affordable alternative to having two separate systems for removing tap water contaminants and preventing limescale build-up.



Using a limescale inhibiting system is a sure-fire way to avoid the many unwanted consequences of limescale deposits without having to worry about ongoing maintenance and wasting water or using electricity.

No chemicals are added to your tap water, no important minerals are removed. With limescale out of the way, clogging issues, and energy inefficiencies are eliminated. Cleaning becomes much easier and you can stop worrying about expensive appliances suddenly breaking down.


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