•1/2 cubic foot of Calcite pH filter media made from naturally occurring calcium carbonate •Slow reaction rate allows for controlled pH correction •Requires 8 GPM per sq. foot of tank area for back washing and 6 GPM service flow rate •Enough media to fill 8" x 44" tank system...see product description for additional tank sizes •Media typically needs replenished annually depending on pH level, water usage, and water chemistry •The bags vary occasionally. Naturally occurring media for neutralization of acidic water. Helps resolve problems with blue/green staining and pin holes in copper pipes. Amount of media required can be determined by tank size: -8"x44" 0.5 ft³ Tank - (1 bag) -9"x48" 1 ft³ Tank - (2 bags) -10"x54" 1.5 ft³ Tank - (3 bags) -12"x48" 2 ft³ Tank - (4 bags) -13"x54" 3 ft³ Tank - (6 bags). If more than 1/2 cubic foot is needed, enter total number of 1/2 pound bags in the quantity. Example...you need 1.5 cubic feet, enter your quantity as three (see tank sizes and amount needed above).