How does a water softener work?

Water softening is a process that involves replacing the calcium and magnesium ions responsible for water hardness with sodium ions. This exchange takes place through a resin made up of small beads that are initially loaded with sodium ions. When this resin comes into contact with hard water, the calcium and magnesium ions attach to the resin, replacing the sodium ions originally present. These sodium ions are then released into the water, resulting in softened water.

For the resin to continue softening the water, it must be “regenerated”. Regeneration consists of washing the resin with salt water (brine). The sodium ions contained in the brine, present in large quantities, gradually replace the calcium and magnesium ions. The resin becomes saturated with sodium ions again and is once more effective at softening the water.

What happens if I do not add salt to my water softener?

If the water softener is not refilled with salt, the resin cannot be regenerated. This means it is no longer cleared of the calcium and magnesium ions it captures from the water. Once saturated, the resin can no longer capture new calcium and magnesium ions, and the softener no longer has any effect: the water leaving the softener has the same composition as the water entering it.
This resin saturation can reduce its quality and may lead to the formation of biofilms, which can encourage microbial growth.