How to Calculate Ion Exchange Resin Life (Tap Water to DI Water)

Contact your tap water supplier (city, municipality, water district) and ask them what the TDS (Total Dissolved Solids) rating is on the water supplied.

For example, your tap water may be 150 TDS.

Divide the TDS (150) by 17.1. This will be the “Grains per Gallon”. In this example that equals 8.8 grains per gallon.

Contact your resin media supplier and determine the grain capacity of each resin tank. Typically, the grain capacity of regenerated resin is about 28,000 gr/cu ft. Assuming you have two 0.5 cu ft resin tanks (1 cubic foot in total), that would produce a grain capacity of 28,000 grains.

Divide 28,000 (resin grain capacity) by 8.8 (grains per gallon of tap water). The answer in this example is a resin capacity of 3,181 gallons of deionized water generation. If your cleaning system uses 15 gallons of water per cycle, one may expect the resins to last for 212 cleaning cycles.

Want more resin capacity, add additional resin tanks. For example, two 3 cubic foot mixed-bed resin tanks have a total grain capacity of 168,000 grains. In this case, using the water consumption above, your tanks will last for 11,200 gallons or 1,272 cleaning cycles.