Granular formula alkalinity increaser. Raises the total alkalinity in your pool water, and also helps keep the pH levels from fluctuating. Low alkalinity levels in swimming pool water can cause undue damage to pool surfaces and equipment. Keeping the alkalinity up helps prolong the life of pool surfaces and equipment, like filter systems, and ensures healthy, comfortable swimming water by protecting against skin and eye irritation. Great for all pool types, including vinyl-lined pools and salt water systems.