Wis. Admin. Code NR § 810.03
The water supplier shall be responsible for ensuring that the public water system is operated and maintained to provide an adequate quantity of safe drinking water to those consumers served by the supplier. This responsibility includes maintaining or contracting for an adequate number of trained staff to perform all duties necessary, performing maintenance and replacement of equipment when necessary to keep the facilities in good operating condition, and providing adequate laboratory testing equipment to control and monitor treatment processes and chemical addition programs. All water suppliers for community systems shall operate the public water system within the design parameters of ch. NR 811 and all parameters of the specific plan approvals for that system. This responsibility also includes ensuring that sufficient fiscal resources are available for adequate operation and maintenance.
Wis. Admin. Code Department of Natural Resources § NR 810.03