A water softener removes calcium and magnesium:
Sodium (Na+1) and chloride (Cl-1) combine, or come together to form sodium-chloride (NaCl) or table salt. Likewise, when salt is dissolved in water sodium-chloride will not be bound tightly and be able to combine with other ions that are looking to attach to either the positive (+1) or negative (-1) electrical charge: Figure 1. Ion:
An ion is a single atom or group of atoms together, which function as a unit. Each ion will have a positive or negative electrical charge; the charge is called a valence; a valence is positive or negative. Things in nature are formed when we match the positive valance with a negative valance: calcium (Ca+2) and magnesium (Mg+2) both have a positive valence of +2. Sodium has a positive valence of +1. chloride has a negative valance of -1.
The Sodium Ion Exchange, an example:
In order to remove the calcium and magnesium from calcium-carbonate or magnesium-carbonate found in the water, we need to give the negative ions they are combined with, carbonate (CO3)-2, something else in exchange for the positive ions. By using an insoluble material the ions may be pulled out of solution and held in place (the resin beads which is made from a plastic material): Figure 2
The exchange process is about the ability of the resin bead to take on one ion while giving up another. Figure 1 shows a resin bead fully loaded with sodium ions, with the calcium and magnesium ions dissolved in the water.
When the resin bead is fully loaded with sodium, it will readily give off the sodium (Na+1) with one positive charge in exchange for calcium (Ca+2) with two positive charges.
When all of the exchange sites are loaded with calcium or magnesium, the resin beads are subjected to a high amount of salt (brine).
The high amount of salt in the brine forces the resin beads to give up the sodium and magnesium that are held at the exchange sites, and take on the sodium ions. The ions are exchanged.
When the unit is rinsed, all of the removed calcium and magnesium, along with the excess salt that forced their removal are washed down the drain. We are left with the charged beads and no excess salt in solution. The soft water contains no additional sodium as the unit is put back on line. No added salt in the water. Do we get sodium from a softener as it is removes the calcium and magnesium ?
Calcium is removed and carbonate (CO3)-2 is left , which takes two sodium ions (Na+1) from the ion exchange resin bead forming sodium carbonate (Na2CO3). Nothing is lost,. The sodium has replaced the calcium or magnesium
The TDS will usually remain the same. However, sometimes additional reactions will raise the TDS. For example, sodium carbonate in water and carbon dioxide (CO2) forms sodium bicarbonate, or (NaHCO3) which will raise the TDS due to the secondary reaction with the formation of an acid from CO2.
How much Sodium do we get from a water softener?
The amount of Sodium in water can be determined by a laboratory water analysis.
Sodium added by an ion exchange water softener can be calculated by multiplying the hardness in the water supply (mg/l as calcium carbonate equivalent) by the factor of .46 to determine the actual sodium (Na) in milligrams added by softening. The harder the original water, the more sodium is added; the sodium replaces the calcium and magnesium (exchanged) in the water.