04 Softener

A softener exchanges the hardness components in the raw water for sodium ions. It is only suitable for water treatment and cannot be used in the aquarium. The softener has nothing to do with a mixed bed filter.

Reverse osmosis systems (also household water devices) can be destroyed very quickly by the formation of lime precipitates and other deposits. The higher the water hardness, the greater the risk of calcification. However, membrane damage can also occur at hardnesses below 5-10°dH. The cause is usually barium in the raw water. Barium forms barium sulphate, which is extremely difficult to dissolve, with sulphate from just a few milligrams per litre.

The water softener is filled with a special ion exchanger that exchanges the hardness components calcium, magnesium, strontium and barium for sodium. As a result, the water is fully softened (extremely "soft") and can no longer damage reverse osmosis membranes. The electrical conductivity is (almost) not changed.
When the capacity of the ion exchanger is reached, the softening system regenerates by flushing down concentrated brine (sodium chloride) to remove the hardness components present at the exchanger. To remove the large amount of sodium chloride, the ion exchanger is briefly rinsed with raw water. To operate a softening system, only the brine tank must be regularly refilled with tablet salt. If the hardness of the raw water changes, the softener must be adjusted to the new value.

If a single softener (usually time-controlled) is regenerating, the connected reverse osmosis system should not be in operation. In a double softening system, also called a pendulum system, softened water is produced continuously. During regeneration of the first resin bottle, the second produces softened water. When the capacity of the second bottle is reached, the system switches back to the first bottle.

It is uneconomical to purchase a softening system only for an aquaristic hobby reverse osmosis system. In addition, the volume-controlled softening systems must be operated with a certain water volume flow so that the built-in water meters work correctly - so the reverse osmosis system must not be too small.
If the water for the entire house is to be partially softened, there should be a junction for the reverse osmosis system between the softener and the blending valve. This way, the reverse osmosis system receives fully softened water and the rest of the house is supplied with partially softened (hardness-reduced) water.