What is the best way to lower the calcium hardness in the water in the pool and the water used to fill it?

The best way to lower calcium hardness in the pool water is to drain the water and refill with water of lower calcium hardness. Have the calcium hardness tested for both the pool water and fill water. Ideal range is 175-300ppm. There are 'calcium reducer' products available through pool stores, but not sure how effective or economical they are.