This article, written by the American Ground Water Trust was originally published in THE AMERICAN WELL OWNER, 2000, Number 2]


The most common water softener for a single family home uses an ion exchange process. The calcium and magnesium ions that make water “hard” are replaced by sodium ions that are obtained from resin in the softening equipment. When the resin can no longer exchange ions, it is usually regenerated by filling the filter containing the resin with a brine solution of concentrated sodium chloride (NaCl / a.k.a. salt). When the resin has been regenerated, the extra brine and the calcium and magnesium from the filter have do be removed. Where does it go? Chances are in rural areas that it goes into a septic system and then eventually into ground water.

Does salt affect the working of the septic system?

Over the last forty years, several studies have shown that normal use of softeners does not adversely affect the working of a septic or aerobic system. Compared with water inputs from laundry and showers, brine disposal does not impose any excess water load on septic systems.

However, some experts believe that brines can reduce the effectiveness of septic systems and that they may cause need for more frequent maintenance. If your water softener has more than 50 gallons of regenerant and uses more than 10 pounds of salt per week, it might be advisable to check that your septic system is big enough to accommodate the salt load without adverse effects on the system’s bacterial processes.

Does extra salt from septic systems cause problems for ground water?

The basic simple answer to the question is that dilution is the solution to pollution. In most areas, the amounts of salt that are added from brine disposal are very small in relation to the total volume of ground water. There have been instances where homeowners, disposing of brines in a dry well close to a shallow water supply well, have experienced occasional saltiness in their drinking water. In some states, dry well disposal is not recommended for brines. Deeper, properly constructed wells are preferable to shallow wells.

The long-term effects of water softener brine disposal on ground water quality are entirely dependent on local geology and the sub-surface hydrologic system. In most cases natural flow of water in aquifer systems will dilute and eventually flush salts. In any event, many places have ground water with natural background levels of both sodium and chloride. The EPA has no specific recommendations for maximum sodium levels in drinking water; for chloride the recommended maximum is 250mg/liter. Drinking water accounts for only a small part of a person’s normal dietary intake of sodium. Milk has about 120mg of sodium per pint and a single slice of white bread can contain over 100mg of sodium.

Compared with saline intrusion of coastal aquifers, soil salinization of irrigation areas and well contamination problems resulting from salt used for road de-icing, water softener salt disposal is not a ground water problem.

[© American Ground Water Trust. This article may be reprinted for non-commercial educational purposes provided it is used in its entirety and that reference is made to its source as an article in THE AMERICAN WELL OWNER, 2000, Number 2]