What Is Bacteriostatic Water (BAC Water) and Why Is It Important? Bacteriostatic Water, commonly known as BAC Water, is one of the most important components used in the preparation of many injectable pharmaceutical compounds supplied in lyophilized (freeze-dried) powder form. It is widely used for the reconstitution of: • Human Growth Hormone (HGH) • Human Chorionic Gonadotropin (HCG) • Peptides such as BPC-157, TB-500, Melanotan 2 (MT2) • Growth factors and other research co