Low alkalinity levels in swimming pool water can cause undue damage to pool surfaces and equipment. HTH PLUS Alkalinity Increaser not only raises the total alkalinity in your pool water, but it also helps keep the pH levels from fluctuating. This 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. HTH PLUS Alkalinity Increaser is great for all pool types, including vinyl-lined pools and saltwater systems.