It is melamine and will turn your pool into a milky mess until it is all filtered out. Also, 1 gal usually only removes about 20 ppm CYA from 10000 gal of water....do the math, 20000 gal pool, 100 ppm CYA, target CYA 40 ppm, need to remove about 60 ppm, price $300 plus shipping! It is not cost effective and it makes the pool so cloudy which is why it is not used very often. Drain and refill is easier, cheaper, and faster!