A new approach to demineralization of marginally brackish waters for individual domestic use has been proposed. An engineering evaluation of the use of various cation exchange resins is given. Primarily the report presents the test results for various commercial resins. The investigation suggests that partial demineralization using a weak acid - weak base ion exchange system should offer simplicity and economy. In order to be satisfactory for domestic use, water need not be completely demineralized, however, in many cases it is desirable to provide more extensive treatment than hardness removal by sodium exchange. A system composed of a weakly acidic ion exchange column in hydrogen ion form and a weakly basic ion exchange column in hydroxide ion form was found to remove an increment of multivalent anions and cations and replace them with an equivalent amount of water.