Combining Water Softener and Septic Tank

Do you live in an area where hard water is one of your plumbing problems?  The commonly recommended solution would be to install a water softening system.  However, there have been concerns on whether such a solution would be applicable for a household that uses a septic system.  This is because it was assumed that water softeners will negatively impact septic systems.

water softener

Water Softening Systems

The excessive levels of calcium and magnesium found in water result in hard water.  The negative ionic charge of water softening systems balance out these minerals formed by positively-charged ions.  As the minerals move through the system they bond with the resin and safely removed from the water.

Since the resin has limited capacity, softening systems need to go through a regeneration cycle.  This will flush the resin using a brine and water solution.  The sodium and potassium ions remove the ions from the resin and sends them into the septic system together with whatever brine and water remains.

To look at the impact of water softening systems on your septic system, let us take a look at a 1970 study by the University of Wisconsin and the National Sanitation Foundation, which was sponsored by the Water Quality Association (WQA).

water softening

Discharge Concerns

The study which is still being cited until today even by many legislators looked at some specific concerns about the discharge made by water softening systems to the septic system.  These discharge concerns include:

  • Bacteria – the bacteria in the septic tank responsible for treating the effluent may be threatened by the salt contents of the discharge from the water softening system. What the research discovered is that the discharge did not cause any negative effect on the anaerobic and aerobic bacterial action. In fact, there were instances wherein the introduction of softened water improved bacterial action.  With the addition of sodium, the less than ideal environment for bacterial growth of hard waste water reached its optimal level.
  • Flow Rate – another point considered was the flow rate of the discharge during the regeneration. The concern was that such regeneration could introduce salt-laden and heavy water too fast and in excessive amounts.  The fear was that the tank may become overloaded or the settling of the solids can be disrupted.  This will cause the solid waste as well as the effluent to be forced into the drain field before it can be completely treated by the bacterial action. According to the research, no overloading of the tank was observed.  Even the entry of dense water had no negative effect on how the stratification and settling process within the tank.  Even other research work sponsored by WQA supports the conclusion.
  • Water Absorption – the salt brine output of the water softening unit may limit the water absorption capability of the drainage field. In turn this will impact the population of the bacteria in the septic system.  The high content of sodium in irrigation systems of some agricultural studies seemed to support this claim.The research work showed though that the increase in the sodium level of the tank’s discharge did not reveal any negative effects on the normal drain field.  Furthermore, the research found out that certain soil conditions got some benefit from it.  The filtration process of the soil improves as the calcium-rich regeneration backwash of the water softening unit flushes down the septic system.

In essence, water softening systems and septic systems can be used together as long as they remain within normal operating conditions and are well-maintained.  Dirty dishes, clogged pipes, and stained clothes can pose more danger to the septic system.

To ensure that your water softening system is configured to work with the septic system properly, consult a licensed professional plumber.