Softened water is drinking water processed to remove high concentrations of dissolved minerals, primarily calcium and magnesium, which cause water hardness. The process aims to prevent scale buildup in plumbing and appliances, but it alters the water’s chemical composition. Many people wonder if this change, specifically the addition of salts, can lead to digestive issues. While generally safe for most, softened water can potentially cause diarrhea or other gastrointestinal upset in sensitive individuals.
The Chemistry of Water Softening
The most common method for softening water is the ion exchange system. Hard water passes through a tank filled with resin beads charged with positively charged sodium ions. The undesirable calcium and magnesium ions are attracted to the resin beads, exchanging places with the sodium ions and releasing sodium into the water supply. The amount of sodium introduced is directly proportional to the original hardness level. Extremely hard water will result in soft water with a significantly higher concentration of dissolved sodium.
The Link Between Softened Water and Digestive Upset
The connection between consuming softened water and experiencing digestive upset, such as diarrhea, is primarily tied to the increase in dissolved salts, most often sodium chloride. This effect is physiological and relates to osmosis in the gastrointestinal tract. Osmotic diarrhea occurs when solutes in the digestive tract are not fully absorbed, creating a high concentration gradient. This high concentration of dissolved sodium or other salts draws excess water into the intestines to balance the concentration. The resulting influx of fluid overwhelms the colon’s ability to reabsorb water, leading to loose, watery stools.
This effect is strongly dose-dependent, meaning it is more likely to occur when the original water source was very hard, resulting in a substantially elevated sodium level. An alternative softening agent, potassium chloride, can also be used instead of sodium chloride. High levels of potassium salts can also have a noticeable laxative effect in the digestive system, similarly increasing the risk of loose stools.
Mitigating Factors and Safe Consumption
For the majority of healthy adults, the sodium added by a water softener poses no health risk and does not cause digestive issues. The sodium content is typically far less than the amount found in a single slice of bread or many processed foods. However, certain populations need to exercise caution regarding consumption.
Individuals on medically restricted low-sodium diets, infants whose kidneys are still developing, or people with kidney disease should monitor their sodium intake from all sources. If a potassium chloride softener is used, individuals with impaired kidney function must consult a physician, as their body may not effectively excrete the added potassium.
A practical solution is to install a dedicated drinking water tap that bypasses the water softener entirely. This dual-tap approach provides the benefits of soft water for bathing and appliances while minimizing the intake of added sodium or potassium. Utilizing a separate filtration system, such as reverse osmosis, on the drinking water line can also effectively remove the added sodium or potassium.