Where does a water system obtain its revenue? A significant portion is from the larger meters. While these meters may be few in number, they can mean a significant difference to a system's revenue and accounted-for water ratios. The larger meters are frequently neglected because they just gradually slow down, rather than stop, and people develop a false sense of security that everything is operating at peak efficiency. An important part of a water system's meter maintenance program should be the testing of the larger meters. In most cases, the most economical approach is to have an on-site meter testing program. This requires investment in the appropriate test equipment, properly designed and constructed meter installations and, most importantly, well trained testing crews. This combination will result in maximum performance from the water meters and optimum returns to the water utility.