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The Impact of Water Softeners on Septic Systems

Posted on by Dennis Hallahan, P.E.

Are water softeners bad for onsite septic systems? There's a lot of negativity surrounding the use of water softeners with an onsite wastewater system, and in searching the internet there are many claims that softeners do not negatively impact onsite systems. So there seems to be the usual conflicting information; let's look more into this issue.

First, confirm with the local code to verify if water softener backwash is prohibited, most states prohibit the discharge of water softeners and other water treatment systems into the onsite wastewater system. If the system is functioning properly then there it may not be an issue. However, if too much salt/brine or other chemicals are discharged into the system it can detrimentally affect the naturally occurring bacteria in the tank and drainfield thereby causing hydraulic overload. In addition to the biological process being affected there are the mechanical issues: the system may be regenerating too often, there may be leaks, there is the extra volume of water, and the mechanical system may be malfunctioning. Given the possible mechanical and biological performance problems Infiltrator Water Technologies recommends discharging water treatment systems to a separate disposal area.

Please contact your local health department for assistance regarding water treatment backwash into your system.

This article offers the following tips to reduce the negative impact of water softeners on onsite septic systems. 

  • Install Modern Water Softeners
  • Substitute Sodium Chloride with Potassium Chloride
  • Set your System's Regeneration Based on Water Flow
  • Only Treat the Necessary Water
  • Get a Bigger Septic Tank
  • Avoid Installing a Leachfield in Soil Containing High Clay Content 
  • Reroute the Backwash Away from the Septic System

About the Author:

Dennis Hallahan, P.E.
Technical Director

Dennis F. Hallahan, P.E., is the Technical Director of Infiltrator Water Technologies. Dennis has over twenty-eight years of experience with the design and construction of on-site wastewater treatment systems. He has authored several articles for on-site industry magazines and has given numerous presentations nationally on the science and fundamentals of on-site wastewater treatment systems. Dennis also oversees a department that is responsible for product research and testing for both Universities and private consultants. The department develops system sizing charts for national and international approvals and assists customers and field representatives in the planning and review of large decentralized systems. He received his MS in civil engineering from the University of Connecticut and his BS in civil engineering from the University of Vermont.  Dennis is a registered professional engineer in Connecticut. He has been with Infiltrator for over 16 years and in his current position as Technical Director, he is responsible for the technology transfer between Infiltrator and the regulatory and design communities. Dennis also holds several patents for on-site wastewater products. Member ASCE, WEF, serves on the NOWRA Technical Practice and  Educational Committees, also on the New England Water Environment Federation’s Small Community Committee.