Weak-acid resin in the hydrogen form was found to effectively remove barium, radium, and hardness, without increasing the sodium content of the product water. The maximum capacity of the weak-acid resin was about 2.3 times that of strong-acid resin, and much less spent regenerant per unit volume of water treated was produced from a weak-acid column than from a strong-acid column. There are, however, some disadvantages to weak-acid ion exchange: swelling of the resin during exhaustion; the need to use acid-resistant materials; the inability to remove noncarbonate hardness; the necessity of stripping carbon dioxide from the product water and adjusting the pH; and the probable higher cost.