From:
http://www.wqa.org/sitelogic.cfm?ID=474
The conclusions drawn from these tests is that softened water is NOT harmful to a normally operating septic system or drainage field. Obviously, this is good news to anyone who has suffered through dingy dishes or clothes, or struggled with precipitate build-up in pipes due to hard water. Homeowners can enjoy all the benefits of soft water without worrying that it will disrupt the efficiency of the household septic system.
From:
http://www.caitechnologies.com/water...ic-systems.htm
Common knowledge supports that higher levels of sodium salt can have a direct impact on bacterial life forms. For instance, most bacteria usually found in fresh water ecosystems would be unable to live in a high salinity environment like an ocean. For this reason, concern was generated that septic systems that rely so heavily on bacterial action may be effected by high concentrations of sodium.
These concerns seem to be unwarranted. First, a typical residential sized water softener discharges between 40 and 70 gallons of water per regeneration. Through much of the regeneration process, fresh water is discharged, containing no salt at all, so the total concentration of salt is very dilute. However, during some stages of regeneration, the sodium concentration can reach as high a 5,000 to 10,000 ppm for brief periods of time.
To see if this level of sodium effected microorganisms typically found in aerobic on-site septic systems, a study was performed that exposed these microbes to a worst case scenario of 10,000 ppm brine solution. The study concluded that “there were no statistically significant differences in the metabolic activity of the microbial community”, and that it was “unlikely that failures in domestic water treatment system are the result of exposure to the brine from home water softeners.” (1)
Other studies indicate that the effect of putting softened water into septic system can actually be beneficial. There is a very low amount of sodium contained in softened water. For every grain of hardness removed, approximately 8 ppm (parts per million) of sodium is added. Although some naturally occurring water sources have very high sodium levels, softened water normally has a slightly elevated sodium level vs. untreated hard water. While this concentration is normally insignificant at typical hardness levels, these higher sodium levels are more in the optimal range for septic system bacterial growth, and can promote bacterial development.(2,7)
From:
http://www.lenntech.com/water-softener-FAQ.htm
7.1 Can brine from softeners damage a septic tank?
The Water Quality Association has performed studies on this subject. These studies have indicated that a properly placed septic tank that works adequately cannot be damaged by brine that is discharged from a water softener. And softened water can sometimes even help reduce the amount of detergents discharged into a septic tank.
From:
http://outreach.missouri.edu/webster...watersoft.html
There are three main questions.
1. Is the softener's salt brine toxic to the septic tank's bacteria?
2. Does the liquid flow rate produced during the softener's regeneration cycle upset the septic tank digestion process and carry over solids into the absorption field?
3. Will the sodium in the brine cause some soils to swell and reduce the water percolation rate through the soil?
Studies by the University of Wisconsin (UW) and the National Sanitation Foundation (NSF) provide some good news. The answers are (1) no, (2) no, and (3) 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. 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.
Keep in mind that an undersized septic tank and/or excessive use of drain cleaners or household antiseptic products are more likely to disrupt the normal operation of a septic tank/absorption field.
From:
http://www.culliganlaredo.com/septic_tanks.htm
First, it was important to study the effect of dissolved salts in softener regeneration effluents on biological action in septic tank systems. These studies demonstrated that regeneration effluent from water softeners had no deleterious effect on the biological action in a septic tank and that the regeneration waste effluents may actually stimulate biological action.
Second, it was felt important to assess the hydraulic effect of the volume of water softener wastewater. These studies demonstrated that the volume of recharge effluent from a water softener is less than that of present day automatic clothes washers. The amount of waste effluent developed by a typical household water softener during regeneration is about 50 gallons. This effluent contains calcium, magnesium, and sodium chlorides. The frequency of regeneration is dependent on water hardness, water usage, and regeneration salt dosage.
Third, the last area of study concerned the effect of softener effluents on soil percolation in septic system drain fields. This portion of the study is important since much of the literature on irrigation contains references to the adverse effects of high sodium water on soil structure and permeability, particularly in clay-type soils. The study concluded that there was an important difference between water softener effluents and sodium effluents, which has an important bearing on soil percolation and permeability.
The important difference is that water softener effluents contain significant amounts of calcium and magnesium and therefore are not really sodium effluents alone. Calcium and magnesium counteract the effect of sodium and help maintain and sustain soil permeability, even in susceptible clay-type soils. Thus, it appears that water softener recharge effluent brine will not affect biological digestion, hydraulic load, or leach field permeability in a septic tank system. However, if the leach field is composed of swelling clays, permeability will be reduced regardless of the presence of water softener effluent. Moreover, calcium and magnesium contained in regeneration effluents actually increased soil permeability.
Salts in the waste effluent from recharge of water softeners created no hydraulic conductivity or percolation problems in a properly designed septic tank seepage field. In fact, it was found that soil percolation was increased by water softener regeneration effluents, as compared to soil receiving household sewage effluents without the addition of effluents from the regeneration of water softeners. In other words, lower hydraulic conductivity (HC) might result if regeneration or recharge wastes from water softeners were not allowed to enter the septic tank seepage field. In this case, the beneficial effects of calcium and magnesium would be lost. This would occur if the regeneration wastes were not discharged to the septic system, but to a dry well, roadside ditch, or other point.
One study was conducted by soil scientists at the University of Wisconsin and dealt solely with anaerobic septic tank systems. The other study, conducted by the National Sanitation Foundation, dealt solely with aerobic septic tank systems.
Conclusions reached in this study were as follows:
Water softener regeneration wastes demonstrated no adverse effects on home aerobic wastewater treatment plant performance, even when stressed by loading at a use rate simulating ten persons (twice the average use rate). There was no difference in performance between days in which the plant received regeneration wastes and days in which it did not.
