Water softeners remove hardness minerals, primarily calcium and magnesium, to prevent scale buildup and improve the efficiency of soap and appliances. While the system is generally safe, potential risks exist concerning the resulting change in water chemistry or failures in system maintenance. For most healthy individuals, properly softened water poses no health risk. Concerns mainly arise for specific vulnerable populations due to added sodium, or from biological issues that can compromise water quality.
How Softening Alters Water Chemistry
The softening process works through ion exchange, which changes the chemical composition of the water. Hard water passes through a tank filled with resin beads charged with sodium ions. As the water flows over the beads, positively charged calcium and magnesium ions (hardness minerals) swap places with the sodium ions. The hard minerals stick to the resin, and sodium ions are released into the water stream, resulting in softened water.
The amount of sodium added is directly proportional to the water’s original hardness level. For example, water with a hardness of 10 grains per gallon adds approximately 18.8 milligrams of sodium to an eight-ounce glass. This is a small amount, equivalent to the sodium found in about one ounce of milk. The system uses a brine solution to recharge the resin, flushing the excess brine and hardness minerals away during the regeneration cycle.
Understanding Sodium-Related Health Risks
The primary health concern related to softened water stems from the increased sodium content, though this addition is negligible for most healthy adults. The average American consumes significantly more sodium from their diet, meaning the water softener contributes a very small percentage to the daily intake. Even with very hard water, the resulting sodium levels are often low enough to be classified as a “low sodium” beverage according to federal food labeling regulations.
The added sodium becomes a concern for specific vulnerable populations placed on sodium-restricted diets. Individuals managing conditions like hypertension, heart disease, or kidney failure must strictly limit sodium intake, and a small, consistent increase from drinking water can be problematic. Infants also require caution, as mixing formula with softened water, especially in hard water regions, can unintentionally increase their sodium consumption.
For these individuals, alternatives may be necessary, such as using a separate, unsoftened tap for drinking and cooking, utilizing a reverse osmosis system to filter the sodium, or using potassium chloride in the softener instead of sodium chloride.
Sickness Caused by System Maintenance Failures
While chemical changes rarely cause illness, a lack of proper maintenance can lead to biological and mechanical failures. The moist, dark, and warm environment inside a water softener tank is an ideal location for microorganisms to proliferate. This can lead to the formation of a biofilm, a slimy layer of bacteria adhering to the resin beads and interior surfaces.
If the system is not regularly sanitized, the biofilm can release pathogens, like Legionella, into the household water supply, especially if water stagnates. Improper maintenance, such as not adding enough salt or allowing a salt bridge to form, prevents correct regeneration. This encourages bacterial growth and reduces the disinfectant residual in the water.
A serious risk is improper installation, specifically failing to maintain an air gap on the drain line. Without this physical separation, a backflow event could draw sewage or wastewater into the brine tank. This contaminates the water supply and can cause severe gastrointestinal illness. Regular professional maintenance, including disinfection and inspection of the drain line, is the most effective way to mitigate these non-chemical health risks.