What is water hardness and how can we solve the problem of limescale?
What is water hardness?
As water moves through nature, it comes into contact with soil and rocks. From there, it picks up various minerals, including calcium and magnesium. This is why even closely located areas can have water of different hardness, and high hardness is particularly common in groundwater and well water.
Water hardness is typically expressed in mg/L or ppm CaCO₃ equivalent, while in Europe, the German hardness unit °dH is often used.
According to the general classification of the USGS (United States Geological Survey):
| Water Hardness | mg/L as CaCO₃ | Approximately °dH |
|---|---|---|
| Soft | 0–60 mg/L | 0–3.4 °dH |
| Moderately Hard | 61–120 mg/L | 3.4–6.7 °dH |
| Hard | 121–180 mg/L | 6.8–10.1 °dH |
| Very Hard | More than 180 mg/L | More than 10.1 °dH |
This is a general indicative classification and not a drinking water standard for a specific country.
How to tell if water is hard?
Often, water hardness is noticeable even without a laboratory analysis. The most common signs are:
- White or yellowish residue on faucets and shower systems;
- Spots on shower glass, dishes, and glass surfaces;
- Rapid accumulation of limescale in kettles, coffee machines, or water heaters; Relatively poor lathering of soap and detergents;
- White marks after water dries;
- Reduced water flow in aerators and showerheads over time.
Leading water treatment companies worldwide identify similar signs as typical symptoms of hard water, but testing is still the best way to accurately determine water hardness.
Why does limescale form?
A portion of calcium and magnesium in water is dissolved and not visible to the naked eye. But when water is heated, evaporated, or dries on surfaces, certain mineral compounds precipitate as a solid residue.
Therefore, limescale is particularly common:
In kettles and coffee machines - water is regularly heated;
In boilers and water heaters - heating surfaces are at high temperatures;
On faucets and showers - water constantly dries on the surface;
In pipes - mineral deposits gradually accumulate over a long period.
The USGS notes that mineral deposit accumulation in pipes can reduce the water flow space, and the layer on heating elements reduces heat transfer efficiency. The mineral layer formed on heating surfaces acts as an insulator and can increase the load on the appliance.
What damage does limescale cause to homes and appliances?
Visible white spots are only one part of the problem.
Plumbing and Faucets
Deposits accumulate in aerators, showerheads, cartridges, and other parts, which can reduce water flow over time.
Boiler and Water Heater
The mineral layer accumulated on the heating element impedes heat transfer between the water and the heating surface.
Washing Machine and Dishwasher
Hard water minerals can accumulate on the water-carrying parts of the appliance and leave spots on dishes.
Is hard water dangerous to health?
Water hardness and water contamination are not the same thing.
Water can be hard and still meet drinking water safety requirements. Calcium and magnesium are essential minerals for the human body, so the presence of limescale itself does not mean that the water is hazardous to health.
On the other hand, low hardness does not automatically mean that water is safe to drink - microbiological, chemical, and other parameters are separate issues.
That is why it is essential to distinguish between water softening and water filtration.
Will a regular filter remove limescale?
This is one of the most common misconceptions.
A mechanical filter removes solid particles such as sand, rust, and various sediments from water, but it cannot retain dissolved calcium and magnesium ions.
By the same principle, standard activated carbon filtration is mainly used to treat other types of impurities and problems related to taste or odor and is not the primary method for removing household water hardness.
Water treatment companies distinguish between filtration and softening: minerals causing water hardness are in a dissolved state, and a regular micron filter is not sufficient to remove them.
How to solve the limescale problem?
If the goal is only to clean already formed deposits, various cleaning agents can be used. However, this removes the symptom, not the cause - if hard water continues to be used, deposits will form again.
If limescale causes problems throughout the house, one of the most effective technologies is an ion exchange water softening system.
The system is usually installed on the central water line of the house so that treated water is supplied to the bathroom, kitchen, boiler, washing machine, and other water-consuming appliances.
How does a water softener work?
A classic water softener works on the ion exchange principle.
A special ion-exchange resin is placed in the system's tank. When hard water passes through it, the resin captures the main causes of water hardness: calcium and magnesium ions, and replaces them with other ions.
After a certain amount of water has been treated, the resin's capacity is depleted, and the system automatically enters a regeneration cycle. During this process, a special brine solution frees the resin from accumulated calcium and magnesium, restoring its operational ability.
In the case of modern automatic systems, this process practically does not require daily intervention from the user - mainly, it is necessary to maintain the appropriate salt level and periodically check the system.
Do all "anti-limescale" systems soften water?
No.
There are water softeners and anti-limescale/water conditioning systems on the market that work on different principles.
An ion exchange softener actually reduces the amount of calcium and magnesium in the water. Some salt-free or antiscale technologies, however, do not remove these minerals from the water - their purpose is to alter their behavior and reduce the formation of deposits on surfaces.
Understanding this distinction is especially important when choosing a system: if the goal is actual water softening and hardness reduction, it is necessary to choose a technology that directly processes hardness salts.
Can reverse osmosis be used against hardness?
A reverse osmosis (RO) system removes a very large portion of minerals from water and consequently also reduces hardness. RO reverse osmosis is one of the effective technologies for reducing substances that cause mineral deposits.
However, household RO is primarily used for drinking water, at a specific point, for example, under the kitchen sink.
If limescale is a problem throughout the house - in the bathroom, boiler, washing machine, and faucets - a central water softening system is a much more practical solution.
How to choose the right water softener?
The selection of a system should not be based solely on its physical size. The actual water hardness, household water consumption, the number of people living in the house, the maximum water flow required at one time, and the volume of the specific system's ion-exchange resin must be considered.
For example, the higher the initial water hardness, the faster the softener's working capacity is depleted, and the more often regeneration occurs.
Therefore, the correct sequence is:
Determining water hardness → Estimating water consumption → Selecting a system with appropriate capacity → Correct installation and programming.
Only after this can it be determined what volume of softener will be optimal for a specific home.
The correct solution against limescale starts with determining water hardness
If limescale constantly accumulates on faucets, showers, kettles, or appliances, simply cleaning it regularly only solves the problem temporarily.
A properly selected water softening system directly addresses the source of the problem - dissolved hardness-causing minerals in the water - and significantly reduces the formation of new mineral deposits.
At AQUAREA, you can choose both household and commercial water softening systems. To select the right system, we first determine the water hardness and consider your actual water consumption and required capacity.