The effect of water softeners on septic systems has been debated since the 1970s. Although some institutions still rely on studies done in the 1970s that suggested there are no adverse effects associated with the use of water softeners, other studies have since suggested that water softeners may cause problems for some septic systems.
A septic system receives waste water from the home and removes harmful pollutants and disease-causing agents such as bacteria and viruses. After treatment, the water is returned to groundwater sources. Typical septic systems include both a tank and a drain field, although some kinds of systems include only a tank that performs all essential functions. Traditionally, most septic systems have been anaerobic, meaning that they work in the absence of added oxygen. However, aerobic systems are becoming more common, and recent studies have suggested that aerobic septic systems may be more susceptible to problems created by water softeners.
A water softener is a device that removes minerals such as calcium and magnesium from water before it is used by a household. It also holds a sodium-based solution, referred to as "brine," in a separate tank for the purpose of occasional cleaning. A water softener changes the water being processed by a septic tank in two different ways: it removes hard minerals from the water normally used by the household, and occasionally discharges a brine solution into the septic system.
Water Softeners and Bacteria
According to the Ontario Rural Wastewater Centre, the increased sodium levels associated with the use of water softeners may harm the bacterial colonies in septic tanks, meaning that they will not function correctly. Similarly, Terry Bounds of Orenco Systems, Inc., has pointed out that septic systems that receive softened water contain more solids. A large number of solids can clog the tank or the drain field pipes and lead to failure of the septic system.
Water Softeners and Concrete Tanks
It has been suggested that the increased levels of sodium created by water softener backwash can increase the rate at which a septic tank corrodes, particularly for concrete tanks. According to the Ontario Rural Wastewater Centre, however, there is no evidence to actually support this claim.
Water Softeners and Water Volume
Another potential problem for septic systems is that water softeners increase the volume of water that flows through the tank and drain field. The Ontario Rural Wastewater Centre maintains that the excess water generated by water softeners does not pose a problem because it is minimal and timed to occur when the septic system is not otherwise being used. On the other hand, the Environmental Protection Agency maintains that excess water from water softeners can pose a problem to septic systems and should be routed away from the septic system.
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