(1) The minimum periodic test interval for gas meters, other than orifice meters, is as follows:

(a) Meters with capacity up to three thousand cubic feet per hour - Every ten years;

(b) Meters with capacity three thousand cubic feet per hour and over - Every five years.

(2) The minimum periodic test interval for orifice meters is as follows:

(a) Differential gauges - At least once each three months;

(b) Orifice plate - At least once each year.

(3) A meter sampling program may be implemented by the utility in lieu of the basic periodic test interval as provided for under WAC 480-90-343, Statement of meter test procedures.