Section R. 460.2356 - Pressure measurement standardsRule 56.
(1) For its working pressure measurement standards, a utility shall have manometers, laboratory-quality indicating pressure gauges, field-type deadweight pressure gauges, or any other instruments that have an accuracy error of not more than 1/2 of 1% of full scale, which shall be used to test the indicating and recording pressure gauges that are used in determining the pressure on the utility's system.(2) For its secondary pressure measurement standards, a utility shall own, or have access to, a pressure-testing instrument that has an accuracy error of not more than 1/10 of 1% of full scale, which shall be used to verify the accuracy of its working pressure measurement standards. An instrument that is used as a secondary pressure measurement standard shall be maintained in an accurate condition.Mich. Admin. Code R. 460.2356