Water Meter Water meter size depends on the application : with smaller 1/2″ to 1″ meters common for residential use, while larger meters (up to 2½” or more) are used for commercial, agricultural, and industrial applications like irrigation THREAD SIZE 1/2″ 15MM 3/4″ 20 MM 1″ 25 MM 2″ 40 MM 2½” 50 MM BSPP/BSPT THREAD