Sodium Bicarbonate 50lb
Easy to use product to control the Alkalinity of your pool water which often gets effected by rain. As a guide only, on average, 1lb of Bi-Carb will raise the Alkalinity of an industry standard pool (12x24, 10,000 gallons) by 10ppm.
If it rains - you need this. Cheaper to buy in bulk than from a pool store in small quantities.