Thursday, June 25, 2009


I hope that Leslie and "Hey Culligan Man..." will forgive any transgressions they may perceive form this missive.

The introduction of sodium chloride (hereafter called salt), in the form of brine from water softener backwash into septic tanks is very questionable at best. There have been claims that excessive levels of salt in effluent will stratify in certain types of drain field soils, and will clog soil pores kinda like biomat, increasing the potential for early failure of drain fields. Reducing the ability of a septic tank to sequester bio-solids in our waste will certainly help shorten the functional life of a drain field. Bacteria are responsible for this sequestration process. Bacteria are responsible for separating settlable and floatable solids, allowing these solids to be retained in the septic tank. Salt and bacteria aren't exactly a good mix.

Septic systems do not function properly if there is a reduction or the outright destruction of bacteria in the septic tank. Salt is a food preservative. It kills bacteria that would otherwise "eat" your food (another way to say this is it keeps food from "spoiling"). You wouldn't want to spoil your septic tank would you? So back washing water softener brine into your septic tank is putting in liquid that has the potential to reduce or outright kill the bacteria in your septic tank. Doesn't make sense that you are often forced to do this by your local officials does it?

Government officialdom often forbids the removal of the backwash from your water softener from your septic tank. They also insist that you do nothing to inhibit the proper function of your septic system. This has always been a head scratcher for me.

The backwash brine from water softeners is loaded with salt (guess that's why its often referred to as brine). The concentrations of salt in the back wash will not only stress the bacteria in the septic tank but the salt will leave the septic tank in the effluent and (possibly) stratify in the soils around the leach lines reducing or even stopping the movement of liquid through the stratified layer. As drain field failure is designed into and expected for conventional, anaerobic septic systems within a couple of decades of the installation, excessive amounts of any material capable of clogging drain field soils potentially decreases the time period to failure. Enter salt, stage left....

There are several products on the market that claim to reduce or mobilize stratified salt that could be clogging soils around drain fields. I personally have never used these products but I have heard of claims of drain fields being very temporarily restored to proper function after application; though there was no proof that the drain field problems were related to salt blockage. The chemicals could perform some other function to temporarily create pourosity in the soil. Most likely these problem sites were a combination of Biomat clogging along with other clogging materials, with salt possibly being one of the materials.

What to do? Well, there are only a couple of choices that are reasonable. If you don't want to remove the backwash from your septic system, switch from sodium chloride to potassium chloride. You shouldn't find a significant difference in water quality. This may not be a perfect answer but it certainly will help. Another, and the most tried and true method for a solution, is REMOVE the backwash from the septic tank and send it somewhere else where it can't cause problems with the proper function and potential life of your septic system!

You should remove the discharge line for the water softener backwash from your septic tank and have it discharge to another place and leave the septic system to handle your biological waste from the home. Installing a small drain field to handle the water softener backwash is easy and relatively inexpensive. After all, the salt is still going into the soil so what's the difference between your septic drain field and a backwash drain field? Interesting designs are available. Let me know of your interest.

Anaerobic conventional septic systems have been historically treated as a dumping place for any type of waste liquid. This is fast becoming a problem for the industry as new standards are being adopted. With the increase for, or outright requirement of, aerobic treatment for septic systems, backwashing water softener brine into septic tanks should be prohibited when aerobic treatment is used. This is still hit and miss with officials.

Basically putting anything into a septic tank that you wouldn't first put into your mouth, or anything that is fundamentally toxic to bacteria, should not be put into septic tanks. Since we have not paid attention to what goes into a conventional septic system until recently, it is difficult to change people’s thinking and behaviors. Fortunately, reasonable amounts of the normal products we use in our homes can go into a septic tank with the rare occurrence of catastrophic consequences. The foundation problem for septic system failure still remains Biomat clogging of infiltrative soils around disposal fields.

Thanks for stopping by.


  1. just one thing to add to your informative article Jerry... I would assume here there most people using septic system and water softeners probably have a well as their water source. (I happen to get city water delivered to my cistern, but I don't think I'm in the majority on this...)

    Anyway - just a word of caution about changing to potassium chloride (actually, two words of caution...)

    1 - regarding brine concentration. Potassium chloride is not a straight one-to-one replacement for sodium chloride (aka "regular" salt.) The brine needs to be about 10% stronger concentration with potassium to do the same function when regenerating the system. If the water softener/condtioner happens to be a Hague Watermax, there is just a button on the controller to adjust. Otherwise, the owner (or their service company) will need to manually adjust the brine concentration to account for the salt change. If this is skipped, incomplete regeneration of their system will occur and eventually, they'll have problems with "slippage" or raw water passing through their system.

    2 - if the well water contains iron - DO NOT USE POTASSIUM. PERIOD. It is NOT recommended EVER for iron-removal systems.

    As always, thanks for being your usual font of information - I just thought these two points should be made before people go making a change to help their septic system, and end up causing a new problem for their water treatment system.


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