Each utility furnishing water service to any of its customers on a metered basis shall, unless specifically excused by the Commission, make provision for a suitable meter testing laboratory and equipment or apparatus as may be necessary to make the tests required by this Part and other orders of this Commission. Meter testing equipment shall, at all reasonable hours, be accessible for inspection and use by authorized representatives of the Commission.
Ill. Admin. Code tit. 83, § 600.300