The Purolite SST family of high efficiency softening resins is based on shallow shell technology. Simply stated, the shorter the diffusion path, the more rapid the softening exchange occurs. This is particularly important during regeneration. Reducing the depth of penetration required to cleanse the resin allows for a more complete regeneration and provides a higher, more efficient utilization of the regenerant. The result is a group of resins with unsurpassed salt efficiency, lower leakage, and reduced rinse water requirements. When compared to conventional softening resins, regenerant reductions of 2 to 4 lbs. per cubic foot of resin per regeneration is possible without sacrificing capacity or increasing leakages. This translates to a salt savings of 700 to 1,400 lbs. per cubic foot per year based on daily regenerations.