Water softeners: what you need to know about salt-softened water

1. The reason given by the WHO

Water softening (with salt) removes the naturally occurring calcium and magnesium responsible for scale in pipes. When these minerals combine with carbonate, they form limescale. To limit buildup, you should keep your hot water temperature below 55°C.

Artificial softening uses ion exchange through a resin: calcium and magnesium ions are replaced with sodium ions. The mineral content remains stable, but the sodium content increases.

The World Health Organization (WHO) recommends drinking naturally soft water, meaning water with a low mineral content. However, it strongly advises against drinking softened water, which is too high in sodium and may be harmful to people with cardiovascular conditions.

The good news: a reverse osmosis system can be installed downstream of a water softener, because the reverse osmosis membrane removes sodium and produces pure, filtered RO water.

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2. More details about water softeners

Maintenance, salt consumption, and a slight increase in water use should be included in your overall budget. On average, a 25 kg bag of salt costs about 10 €, and a family of 4 in an area with hard water uses nearly 5 bags per year. Maintenance is easier with Oja water softeners, which have a cleanable pre-filter. The additional water use for rinsing the resin ranges from 5 to 10 %, and the wastewater contains chlorides, which are not environmentally friendly.

Despite the initial investment, a water softener helps you save money over the long term: less detergent, soap, and laundry detergent, along with lower electricity consumption thanks to improved energy efficiency.

Some retailers recommend installing a reverse osmosis system after a water softener to protect the RO membrane. Soft water does extend the membrane's lifespan, but it is not essential: a home RO system can handle hardness up to 40°f.

3. Maintenance considerations

Annual maintenance is recommended to check that the valve and bypass are properly adjusted. To ensure high-quality tap water, check the salt level regularly and perform a hardness test at least once a year. This helps prevent water that is too hard (ineffective softening) or too soft (potentially corrosive).

4. Eco-friendly alternatives to salt-based water softeners

More eco-friendly solutions are available to combat limescale without salt:

• Electromagnetic systems: they change the structure of limescale crystals to prevent them from adhering, without changing the water's chemical composition. No wastewater or maintenance is required.
• CO₂ softening: this method converts carbonate into bicarbonate without removing calcium or magnesium. It produces no wastewater, uses no salt, and the water remains fully drinkable.

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