SeaKlear Calcium Increaser, 1 Quart Bottle Boosts calcium levels in soft water Prevents damage to spa equipment from aggressive water Proven effective & reliable Made in the United States Boosts calcium levels in soft water Prevents damage to spa equipment from aggressive water Proven effective and reliable 1-ounce of spa calcium increaser per 500-gallon of water increases hardness by 7 ppm Made in the United States