Best McGowan Water! Missoula Water Conditioning & Quality Testing. We’re a local, family-owned business that has been in operation since 1968. We provide water treatment services to Missoula, MT and the surrounding areas. McGowan Water Conditioning has been helping Missoula, MT residents for over 50 years by providing expert services in the areas of water conditioning, water filtration, and water quality testing. Water is essential to life and we believe in protecting this precious resource for our local community and for future generations. Address: 101 N Grant St, Missoula MT Phone: (406) 728-3590