Replenish, 4 L / 1 fl. gal. Replenish is a proprietary blend of salts designed to replenish physiologically relevant minerals that are removed by reverse osmosis filtration Replenish restores general hardness (GH) using a balanced blend of both soft (sodium potassium) and hard (calcium magnesium) salts Restoration of mineral content is essential since a complete lack of minerals will result in osmotic stress