Wis. Admin. Code Department of Natural Resources NR 810.10
For community water systems, the system pumps, the distribution system and related storage facilities shall be operated to maintain a minimum of 35 pounds per square inch and a maximum of 100 pounds per square inch at ground level above the water main at all locations in the distribution system under normal operating conditions. Normal operating conditions include the peak hour demand on the maximum day. Where the storage or primary pumping facilities cannot provide a minimum static pressure of 35 psi throughout the distribution system at street elevation it shall be necessary to create a boosted pressure zone to serve those portions of the system. The use of pressure boosting systems on individual service lines shall be limited to a maximum of 10 individual systems in any given service area. The individual pressure boosting systems shall be owned and maintained by the public water system owner. The department may require pressure testing to determine whether adequate pressures are available. In situations where static pressures exceed 100 psi, pressure reducing devices may be required on mains in distribution systems having documented system deficiencies or problems due to high pressure such as main breaks and service line breaks.
Wis. Admin. Code Department of Natural Resources NR 810.10
Section SPS 382.40(7) (d) 2. a. requires a pressure reducing device to be installed to protect individual services when the incoming pressure exceeds 80 psig.