(1) A gas utility must state in its tariff the minimum heating value of gas delivered to customers. The minimum heating value of the gas must be sufficient to operate an appliance uniformly.

(2) Testing equipment. If a gas utility provides and maintains its own gas calorimeter, the calorimeter and accessories must be installed in a suitable area. The calorimeter and its location and accuracy must be approved by the commission.

(3) If a gas utility does not maintain its own gas calorimeter, the utility's supplier must provide the calorimetric results to the commission on request.

(4) A gas utility may use a caloroptic indicator to determine the heat value when a mixture of liquified petroleum gas and air is used.

(5) Testing requirements. Each gas utility must take at least one daily heat value test of the gas supplied to its customers.

(6) The total heating value must be stated in British thermal units per cubic foot.

(7) The average daily heating values must be determined by taking the average of all daily heating values measured throughout the day. The average monthly heating value must be the average of all daily average values for the calendar month.

(8) For billing purposes, the gas utility may apply the average heating value for a given month to the following month provided the procedure is written in the utility's tariff.

(9) Testing records. Each gas utility must keep complete records of each heat value test. These records must be accessible to the commission and its authorized representatives.

(10) The utility must adopt standard forms that record the heating value, gas analysis, and specific gravity results. The forms are subject to commission approval. Each form must be retained as a record for at least two years at the station where the tests were made.