100. DEFECTS AND ERRORS IN MEASUREMENTS No service water meter shall be allowed in service which has an incorrect gear ratio or dial train or is in any way mechanically defective or shows an error in measurement in excess of three (3%) per cent, plus or minus, when registering water at stream flow equivalent to approximately one-tenth, one-half and full normal rating under average service pressure. However, a water utility may, with the approval of the Commission, follow the American Water Works Association's standard procedure for testing water meters.105. ADJUSTMENT When adjustment is necessary, such adjustment shall be made as accurately as practicable for average rate of flow under actual conditions of installation. Test for accuracy shall be made with suitable testing device in accordance with the best modern water meter practices,110. AVERAGE ERROR For purposes of application, the average error of a water meter is defined as one-third of the algebraic sum of the errors when tested in accordance with Section 100 above, provided, however, that a water utility may, with approval of the Commission, follow the American Water Works Association's standard procedure for testing water meters.