Water Softeners and Septic Tank or Sewage Treatment Systems

The effect of water softeners on sewage treatment plants

Many homes in hard water areas have water softeners.  Water softeners reduce the amount of Calcium in the water, making it soft.  Les detergents, shampoos etc. are needed and in this respect, water softeners help the septic tank or sewage treatment plant.

Problems with water softener salt regenerant

However, the regenerant or backwash water from the water softener contains massive amounts of salt and this brine must not be discharged into the septic tank or sewage  plant as it will 'pickle' the tank, killing the beneficial bacteria that break down the sewage.

Many water softener suppliers and even the Trade Bodies will tell you that water softener regenerant is safe for septic tanks and sewage treatment plants, but research has shown this not to be true.

Research in the USA has focused on water softener discharge of regeneration brine and their statement is "Our experience with regard to the operation and maintenance of systems that discharge water softener backwash to septic tanks is that it has a detrimental effect on the effluent that is discharged."

As a result, the disposal of water softener backwash into the septic tank system has been banned in many States including Texas, California, Conneticut, Massachusetts, Michigan, New Jersey and all States in the Northeast and Southeast.  This has not been done lightly with no evidence of harm done to the performance of the system.

Most reputable sewage treatment plant and septic tank manufacturers will not allow the regenerant from water softeners to be discharged into their tanks and their warranties are null and void if this happens.  The answer is to direct the backwash water into the surface water drains which should not be connected to the sewage system.