Do Water Softeners Hurt Septic Tanks?

Do Water Softeners Hurt Septic Tanks blog header

From time to time, we’re asked the question, “Does using a water softener have an adverse effect on household septic tanks?”

Since one quarter of all homes in the U.S. have a septic system and we know that hard water affects nearly 85 percent of homes in the country (many of those homes have or need a water softener), that’s a very valid question. 

Let’s break down this question to more specific issues:

Is a water softener’s brine tank discharge toxic to the septic tank’s bacteria?

Studies by the University of Wisconsin (UW) and the National Sanitation Foundation (NSF) found that the answer is “no”. UW and the NSF found that the increased sodium in the softened water was actually helpful to the bacterial organisms in the septic tank, and did not hurt the soil’s ability to absorb water in a normal absorption field.”

Does the flow rate produced during the softener’s regeneration cycle upset the septic tank digestion process and carry over solids into the absorption field?

Again, the answer is “no”. The volume of softener backwash during regeneration was easily within the limits of what the septic tank could handle. An automatic washer would pose a greater threat to the septic tank than a water softener. The calcium-rich backwash acted similar to gypsum, which is a high-calcium mineral long used to increase the porosity of clay soils.”

To ensure that your regeneration settings are correct and that your water softener is not pumping unnecessary water into the septic system, be sure to have your softener checked out by a water treatment professional on a regular basis.

Can Water Softeners Actually Provide Advantages to a Septic System?

The answer is “yes”. 

Recent studies found that with softened water, consumers can cut back on soap usage by 50 percent and dishwashing detergent by 70 percent[i].  Because household cleaning products (shampoos, harsh laundry detergents and bleaches) can disrupt the normal operation of a septic tank and absorption field, the reduction in soaps and detergent usage can be a big advantage for a septic system.

The Water Quality Association shares another advantage in using a water softener with a septic system:


If you have or think you may have hard water, download WaterTech’s Hard Water Guide:

Hard Water Guide cta

[i] The Energy Savings Study was conducted in 2009 in conjunction with theBattelle MemorialInstitute and funded by theWater QualityResearch Foundation. The Detergent Savings Study was conducted in 2010 in conjunction with Scientific Services S/D, Inc. and funded by theWater QualityResearch Foundation.


One comment

  • This is a actually a question I’ve been curious about for a while with my water softener. My septic system has been giving me issues over the years since I got my water softener installed. I’ve even had to call a plumber a few times to handle some major issues as well. Thanks for posting these things to look out for with septic systems when you get a water softener!