Mich. Comp. Laws § 288.631

Sec. 71. (1) All dairy products shall be tested at a minimum frequency of 4 out of every 6 months, or as determined by the director. (2) Except when the water supply is required to be tested annually as provided in section 130(9)(h), well water samples for dairy farms shall be tested a minimum of once every 3 years and found to be of safe and satisfactory quality. (3) Water supplies for dairy plants shall be tested a minimum of once every 6 months. (4) Recirculated water or recirculated cooling medium shall be tested a minimum of once every 6 months. (5) Condensate recovery water shall be used only in applications that conform to requirements and procedures accepted by the United States food and drug administration or the director.