What Types of Salt for Water Softeners Are Safe for Septic Systems?

Evaporated salt comes from underground salt deposits that are mined and later evaporated.salt mining image by jesse welter from Fotolia.com

Septic systems are like tiny sewage treatment plants built into a house. Septic systems consist of anaerobic bacteria that decompose or mineralize the waste that enters the system from the house. Some substances can cause trouble for a septic system. Certain types of salt can lead to a buildup of waste in the system, so it's important to know which salts cause these problems when softening water.

Types of Salt

The three types of salt used in water softeners are solar, rock and evaporated. Rock salt is naturally occurring salt. Solar salt is created when sea water is evaporated. Evaporated salt comes from underground salt deposits that are mined and later evaporated. The cheapest of the three, rock is more prone to build-up and system cleaning. Evaporated salt is the most soluble and the strongest at softening hard water. Evaporated and solar salt are more recommended for septic system safety than rock salt because of the build-up problems.

Potassium chloride is another salt that can be used to soften water. Potassium chloride acts differently than the other salts (mostly sodium chloride) because it replaces hard water minerals with potassium instead of sodium. Potassium chloride is often used when a family member is on a low sodium diet. Potassium chloride doesn't act much differently on septic tanks than sodium chloride. Too much salt may affect bacteria growth in the tank, but potassium chloride is typically more soluble than sodium chloride, so it dissolves more quickly and will likely have less effect on septic tanks. Potassium chloride is more expensive than sodium chloride.

Studies compiled by CAI Technology show that water softening salt may improve the functioning of a septic system instead of harming it. Because of the amount of water discharged each day (40 to 70 gallons), the water rarely reaches a high enough salt concentration to affect bacteria growth. The salt concentration may even be more beneficial to bacteria growth and system percolation. If these studies are indicative of standard septic system behavior, almost all water softening salts would be safe for septic systems.