One cartridge is rated for around 400 gallons of water at the 6 ppm Total Dissolved Solids (TDS) purity level, which meets manufacturer specifications for Iron Edison’s Industrial Series Nickel Iron batteries. A cartridge has a one year shelf life.
The actual life of a cartridge will vary depending on the quality of your water. Ask an Iron Edison system designer for a complementary water analysis, completed by Philadelphia Scientific, which will produce a report on what your cost per gallon of water would be using the Deionizer system. It’s likely less than the price of store-bought distilled water.