CQWA POSITION PAPER ON
SEPTIC TANK EFFLUENT DISPOSAL

The Canadian Water Quality Association has consistently held the position that discharge from water softener devices into private sewage disposal systems does not harm the septic environment.

The experience of the water treatment industry, available literature and recent studies have shown that the waste waters and mixed brines from filters and water softeners have no significant effects on such sewage disposal systems.

Two years ago, the U.S. Environmental Protection Agency (EPA) confirmed the viewpoint of the CWQA that softener regeneration wastewater is not harmful to septic systems. A document, entitled “Onsite Wastewater Treatment Systems Special Issue Fact Sheet 3” supports the CWQA on its affirmation that softener effluent has no deleterious effect on these systems. We have attached this document for your information and review.

The EPA Fact Sheet concluded that:

• High concentration of calcium and manganese in the softener backwash water may, in fact, be helpful rather than harmful;

• No hydraulic overload problems are caused when additional volume of wastewater (about 50 gallons per regeneration cycle) is added to the wastewater stream;

• The calcium and manganese ions in water softener effluent affects the soil structure in the soil absorption field positively rather than negatively.

In recent years it has become our experience that provincial and municipal regulatory agencies have from time to time banned discharges from water conditioning equipment into private sewage systems. This is despite the evidence, which shows that there is no deleterious effect.

CWQA POSITION:

The disposition of waste waters and brines from the backwashing and regeneration of household water conditioning equipment to private sewage disposal systems is an economical practice and is in the best interest of the equipment user. Experience of the industry, available literature and recent studies have shown that the waste waters and mixed brines from filters and water softeners have no significant effects on such sewage disposal systems.

SUMMARY:

The question of the effects of water softeners on septic tank systems is not a new one and as a result, CWQA has collected a considerable amount of reference material on the subject. Existing data is summarized in the WQA paper, "Effects of Backwash Water and Regeneration Wastes from Household Water Conditioning Equipment on Private Sewage Disposal Systems".

Because of their lack of knowledge on the subject, a number of provincial and local regulatory agencies has from time to time proposed restrictions which would ban discharges from water conditioning equipment to private sewage systems. In several cases, the presentation of factual information through local groups has led to the withdrawal of adverse regulations but, in other areas, pressure to regulate the discharges still continues. To gain additional support and documentation for the CWQA position, the Water Quality Research Council (WQRC) has supported two studies, one primarily directed at aerobic treatment systems at the National Sanitation Foundation. The resulting data will be used to inform interested persons and agencies whenever the question is raised.

REFERENCES:

* University of Wisconsin Study "Potential Effects of Water Softener Use on Septic Tank Soil Absorption On-site Waste Water Systems".

* National Sanitation Foundation Study, ‘The Effect of Home Water Softener Waste Regeneration Brines on Individual Aerobic Wastewater Treatment Plants".

QUESTION: Does a water softener have any harmful effect on a septic tank?

ANSWER: The backwash and brining effluents from a softener can be discharged into a septic tank. The latter should, however, be properly installed and of adequate size to ensure satisfactory results. Proper sizing of the septic tank is highly important. While many states recommend units with a minimum of a 500 gallon capacity, even smaller units may provide adequate liquid capacity in relation to the amount of salts discharged by the softener.

Many public health authorities recognize that softener regeneration wastes can be safely discharged into septic tanks.

The Public Health Service in a "Manual of Septic Tank Practice" writes: "Waste brines from household water softener units have no adverse effect on the action of the septic tank but, may cause a slight shortening of the life of a disposal field installed in a structured clay-type soil."

From this, it is evident that the type of soil in which the disposal field is situated must be taken into consideration.

High concentrations of sodium salts deposited in certain types of soil over a period of time would result in loss of permeability. When this occurs, the soil cannot absorb and transmit the waste water. As a result, the absorption capacity of the drain field gradually decreases.

On the other hand, the calcium and magnesium ions discharged by the softener may tend to open up the soil, reversing the clogging action of the sodium salts.

To date, there are no reports on file of the failure of a distribution field to absorb the sodium salts due to softener regeneration wastes.

In the event a serious doubt exists regarding the effect of the sodium wastes on the distribution field, the brine could be discharged into a dry well. Generally, a dry well (a hole filled with course gravel) will serve for many years. However, the use of a dry well should be necessary only in extremely few instances.

There is some advantage in the use of fully automatic softeners where the discharge into the brine tank may be a problem. These softeners can be set to recharge frequently but, with smaller amounts of salt.

Fully automatic softeners use from 40 to 80 gallons of water per recharging. With the operation requiring about one hour, the water flow rate is low. Further, the process is normally set to occur between midnight and 5:00 a.m., a time when little or no water is being used in the house. Under these conditions, a softener places far less burden on the capacity of the septic tank than do such water-using appliances as automatic dishwashers, washing machines or toilets, etc.