Salt softeners and CO₂ softeners both aim to reduce limescale in water, i.e. by removing the excess limescale and magnesium responsible for scale deposits. However, they work differently and have varying impacts on water and the environment. The aim of this article is to explain the advantages and disadvantages of each one, so as to guide you towards your ideal choice.

 

1. CLASSIC SALT SOFTENER

 

1. 1. Process

 

• • Ion exchange: the key to the process

The salt water softener is placed right at the central water inlet. The water passes through a first compartment equipped with a sodium-loaded ion exchange resin. This resin captures calcium and magnesium ions in the water and replaces them with sodium ions. The outgoing water is thus depleted of magnesium and calcium and replaced by sodium. The mineral composition of the water is altered to prevent scale formation.

 

• • The regeneration cycle

After a while, the resin becomes saturated with calcium and magnesium ions, and is depleted of sodium. It then loses its effectiveness. To restore its softening power, the unit regenerates the resin by injecting a brine solution (salt water). This operates the reverse exchange, and the resins discharge calcium and magnesium ions to regenerate sodium. The softener is then ready to operate again.

 

• • Rinse water drainage

The water used for regeneration is salty, loaded with dissolved minerals and discharged into the wastewater. A salt water softener therefore requires drainage.

As an example, a 20L resin softener discharges 100L/regeneration cycle. With a regeneration cycle every 5 days, i.e. 73 cycles/year, around 7,300L of water/year are discharged.

 

1. 1. Advantages and disadvantages

 

• • Benefits :
    

     

    • • Reduce limescale in water and systems Extend the life of household appliances
    • • Softer skin and hair after showering
    • • Reduced consumption of detergents and household products
    • • Energy savings thanks to more efficient heating equipment

 

• • Disadvantages :
    

     

    • • Salt consumption and regular maintenance (which involves a cost)
    • • Saline wastewater discharge
    • • Mineral depletion. This can make the water too poor for drinking. The addition of an osmosis unit with remineralization cartridge is recommended.
    • • Water that is too soft (low in minerals) can promote corrosion of metal pipes.
    • • Increased sodium content in water. This may change the taste or be a disadvantage for people on a low-salt diet.
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2. CO ECOLOGICAL SOFTENER₂

A CO₂ softener is an environmentally-friendly alternative to salt softeners for reducing limescale in water without altering its mineral composition. Its operation relies on the injection of carbon dioxide (CO₂) into the water to transform limescale into soluble bicarbonates.

 

2. 2. Process

 

• • CO₂ injection in water

The softener is equipped with a regulator and a CO₂ bottle, similar to those used for beverage carbonation. As water passes through the device, a controlled amount of CO₂ is injected.

 

• • Transformation of limestone into bicarbonates

Once dissolved in water, CO₂ reacts chemically with calcium carbonate (CaCO₃), responsible for scale formation. This chemical reaction produces calcium bicarbonates (Ca(HCO₃)₂), which remain dissolved in the water and do not build up on pipes and appliances.

Unlike a salt softener, this system does not remove essential minerals such as calcium and magnesium, but prevents them from precipitating as scale.

 

2. 2. Advantages and disadvantages

 

• • Advantages :
    

     

    • • Environmentally-friendly: No discharge of saline wastewater
    • • Easy maintenance: No salt to refill, only the CO₂ bottle needs to be replaced periodically.
    • • Preserves minerals: the water retains its health-giving calcium and magnesium.
    • • Compatible with drinking water: No increase in sodium content.
    • • Easy installation: Connects directly to the main water supply.

 

• • Disadvantages :
    

     

    • • Higher initial cost than a conventional softener.
    • • Need to recharge in CO₂
    • • Does not completely reduce water hardness, but prevents scale formation.
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3. CONCLUSION: WHICH SOFTENER TO CHOOSE?

 

• • Choose a salt water softener if :
    

     

    • • You want totally softened, limescale-free water.
    • • You accept more frequent maintenance and salt water discharge.
    • • You have pipes suitable for softened water (to avoid the risk of corrosion).

 

 

• • Opt for a softener in CO₂ if :
    

     

    • • You're looking for an ecological solution that doesn't require salt or heavy maintenance.
    • • You want to preserve minerals that are beneficial to your health.
    • • You want a simple, compact installation with reduced environmental impact.