By Jerome Fife
The practice of introducing sodium chloride — commonly known as salt — in the form of brine from water softener backwash into septic tanks raises serious concerns. There are assertions that high concentrations of salt in effluent can accumulate in certain drain field soils, leading to clogged soil pores similar to biomat, which could hasten the failure of drain fields. This interference with a septic tank’s ability to manage bio-solids can significantly reduce the lifespan of a drain field. The bacteria present are crucial for this process, as they help separate and retain settleable and floatable solids within the tank. Unfortunately, salt and bacteria do not coexist well.
Septic systems rely on healthy bacteria to function effectively; any decrease or elimination of these microorganisms can disrupt their operation. Salt acts as a food preservative, killing bacteria that break down organic matter (essentially preventing food from spoiling). You wouldn’t want to spoil your septic system, would you? Therefore, introducing water softener backwash into your septic tank means adding liquid that could diminish or eradicate the beneficial bacteria present. It’s perplexing that local authorities often mandate this practice.
Regulatory bodies often prohibit the removal of water softener backwash from septic tanks while simultaneously insisting on maintaining the proper operation of septic systems. This contradictory stance has always puzzled me.
Water softener backwash is rich in salt (hence its designation as brine). The high salt concentrations can stress the bacteria in the septic tank and may also exit the tank with effluent, potentially stratifying in the soil surrounding leach lines. This can hinder or completely block liquid movement through the affected layers. Given that conventional anaerobic septic systems are designed to fail within a couple of decades, introducing excessive materials that could clog drain field soils shortens this timeline. Enter salt…
There are various products available that claim to reduce or dislodge salt stratification that might be obstructing drain fields. While I haven’t personally used these products, I’ve heard anecdotal reports of temporary restorations of drain field functionality post-application; however, there’s no solid evidence linking these issues directly to salt blockage. It’s possible these chemicals create temporary porosity in the soil for other reasons. Most likely, these problematic sites experienced a combination of biomat clogging and other materials, with salt being one of many factors.
What are your options? There are a couple of sensible approaches. If you prefer not to remove backwash from your septic system, consider switching from sodium chloride to potassium chloride. This shouldn’t significantly impact water quality. While it’s not a perfect solution, it may help. The most reliable solution is to eliminate the backwash from the septic tank entirely and direct it elsewhere to prevent issues with your septic system’s efficiency and longevity.
You should reroute the water softener backwash away from your septic tank, allowing the system to focus on processing biological waste from your home. Installing a small drain field specifically for the water softener backwash is straightforward and relatively affordable. After all, the salt will still enter the soil; what’s the real difference between your septic drain field and a dedicated backwash drain field? There are some creative designs available if you’re interested.
Traditionally, anaerobic septic systems have been treated as dumping grounds for all sorts of liquid waste. However, as new standards emerge, this practice is becoming increasingly problematic. With a shift towards aerobic treatment systems, it should be prohibited to backwash water softener brine into septic tanks when such treatments are in use — a point that remains inconsistent among officials.
Essentially, anything you wouldn’t put in your mouth — or anything harmful to bacteria — should not be added to a septic tank. Since we’ve largely overlooked what enters conventional septic systems until recently, changing public perception and behavior proves challenging. Fortunately, typical household products can generally be introduced into a septic tank without severe repercussions. The underlying issue leading to septic system failures continues to be biomat clogging in the infiltrative soils surrounding disposal fields.