Water Softeners and Water Treatment Systems
Home water softeners, which periodically generate a backwash that is high in sodium, magnesium, and calcium concentrations, can affect waste water treatment processes and the composition and structure of the infiltration field biomat and the underlying soil. However, attempts to predict whether impacts will occur and to estimate their severity are difficult and often inconclusive.
The following is from the Connecticut Department of Public Health publication PRIVATE DRINKING WATER IN CONNECTICUT, Hardwater – Softeners, Facts and Issues
Backwashing of a softener to a septic system is specifically prohibited in the CT Public Health Code section 19-13-B103 and in the Technical Standards for Subsurface Sewage Disposal Systems. Discharging the backwash to a separate dedicated system is a viable option and is under the authority of the CT DEP, pursuant to Section 22a-430 of the CT General Statutes. For information on recommended disposal alternatives call CT DEP at (860) 424-3018. It is common practice in CT to use softeners for iron/ manganese removal, which this office does not support. There are better treatment techniques available for iron/manganese removal without the addition of any chemicals.
Water softeners remove “hardness” (dissolved calcium and magnesium) through ion exchange processes. Incoming hard water passes through a tank of containing high-capacity ion exchange resin beads supersaturated with sodium. The calcium and magnesium ions in the water attach to the resin beads, replacing the sodium, which is released into the water. The softened water is then distributed for use throughout the house.
The effects of flushing the effluent from water treatment systems into the septic system may best be termed controversial. As stated above in Connecticut this practice is forbidden by CT Public Health Code and the Connecticut General Statues.