Type of Submeter. All submeters installed in compliance with these regulations shall be of a type and class to properly and accurately register gas consumption. A submeter installed for billing purposes shall have been approved by the Commission. Charges for Gas. All charges for gas used by an occupant shall be calculated from the readings of the occupant's submeter. Meter Accuracy. All submeters in service shall be tested by the owner as provided by this chapter. Fast Submetering. If an occupant's submeter is found to be more than 2 percent fast at check flow, the owner shall: Recalculate the occupant's bills for the lesser of the period of the occupant's service or the period since the submeter was last tested: Make a refund or a credit to the occupant, if the adjustment so calculated exceeds $1. Slow Submeter. If a submeter is found to be more than 2 percent slow at check flow and the unbilled amount exceeds $5, the owner may bill the occupant 1/2 of the unbilled error for the period of the occupant's service, or since the submeter was last tested, whichever is less, not for a period longer than 12 months. Overcharge Adjustment. If an occupant has been overcharged as a result of an incorrect submeter reading, incorrect calculation of the bill, or incorrect submeter connection, the owner shall credit or refund the amount of overcharge to the occupant. Undercharge Adjustment. If an occupant has been undercharged as a result of an incorrect submeter reading, incorrect calculation of the bill, incorrect submeter connection, stopped submeter or similar reasons, the amount of undercharge may be billed to the occupant. Meter Test by Owner. Upon application by the occupant, the owner shall test the submeter for accuracy, at a laboratory approved by the Commission, with no charge to the occupant, provided that a test was not made in the past 18 months. Testing upon Installation and Removal of Meters. A submeter may not be placed in service until it has been tested and approved by the owner at a laboratory approved by the Commission to an accuracy of 98.5—100.5 percent. If a submeter is removed from service or replaced by another submeter, it shall be properly tested and adjusted by the owner at a laboratory approved by the Commission before being placed in service again.