Calculating daily softening demand
Daily demand (grains per day) = people in household x daily gallons per person x water hardness in GPG. Example: 4 people x 75 gallons per day x 15 GPG hardness = 4,500 grains per day. An APEC 48,000-grain softener at this demand provides approximately 10 days between regeneration cycles (48,000 / 4,500 = 10.7 days). Aiming for 7-14 day regeneration intervals optimizes resin utilization -- too-frequent regeneration wastes salt; too-infrequent regeneration can allow slight hardness breakthrough near the end of the capacity cycle. A 48,000-grain unit suits most 3-4 person households with hardness up to 20 GPG. A 64,000-grain unit is appropriate for larger households or hardness above 20 GPG.
Iron content and softener selection
APEC softeners remove up to 3 PPM clear water (ferrous) iron. Above 3 PPM iron, or in the presence of oxidized (ferric) iron (rust particles in water), a dedicated iron pre-filter should be installed upstream of the APEC softener to protect the resin from iron fouling. Iron fouling permanently reduces resin capacity and cannot be reversed by standard salt regeneration. APEC sells compatible whole-house iron filters for pre-treatment in high-iron applications. Test water for iron content (a mail-in water test for $25-50 provides comprehensive results) before sizing the softener system.
Pairing APEC softener with APEC RO system
APEC recommends connecting the RO system to the softened water supply rather than the unsoftened supply. Softened water extends RO membrane life by preventing calcium carbonate scaling on the membrane surface, which is the primary cause of premature RO membrane failure in hard water applications. The APEC ROES-50 standard 5-stage RO system (75 GPD, 3.2-gallon tank) is the baseline model for kitchen sink installation. The ROES-PH75 adds a 6th alkalizing stage (calcite remineralization) that adds back calcium and magnesium after RO filtration, providing the mineral taste of spring water without the hardness-causing concentrations present in untreated supply water.
Water test before APEC softener purchase
APEC recommends conducting a basic water test before purchasing any softener. The minimum parameters to test are: hardness (GPG), iron (PPM), manganese (PPM), pH, and TDS. A municipal utility annual water quality report provides hardness and iron data for free. For private well users, a comprehensive mail-in test from a certified laboratory (National Testing Laboratories, Culligan, or similar) provides all necessary parameters. Results from this test determine the appropriate APEC softener capacity, whether an iron pre-filter is needed, and whether an additional RO system addresses residual concerns in drinking water.