Section NR 811.70 - Water main design The design of water mains and distribution systems shall meet the following requirements:
(1) GENERAL. Water mains and water distribution systems shall be designed and operated to maintain point-of-entry water quality. Special consideration shall be given to distribution main sizing, providing multidirectional flow when possible, providing an adequate number of shut-off valves for distribution system control, providing an adequate number of fire hydrants where fire protection will be provided, and providing for adequate flushing throughout the system. Systems shall be designed to maximize turnover, to minimize the number of dead ends, and to minimize residence times while delivering pressures and flows meeting the requirements under subs. (4) and (6).(2) FLOODING. Any areas of the project which are located within the floodway, as defined in s. NR 116.03 (22), or floodplain as defined in s. NR 116.03 (16), shall be identified on the plans and shall conform to the requirements of that chapter. Note: Refer to ch. NR 116 for floodway and floodplain requirements.
(3) WETLANDS. Any areas of the project which are to be located within a wetland, pass through a wetland or may impact a wetland shall be identified. Note: Copies of the Wisconsin wetland inventory maps are available for inspection at the office of the department of natural resources and may be purchased through the department's internet web site.
(4) PRESSURE. All water mains, including transmission mains and those not designed to provide fire protection, shall be sized after a hydraulic analysis based on flow demands and pressure requirements. The minimum and maximum normal static pressure in the distribution system shall be 35 psi and 100 psi, respectively, at ground level. The system shall be designed and operated to maintain a minimum residual pressure of 20 psi at ground level at all points in the distribution system under all conditions of flow.(5) DIAMETER. The minimum diameter of water mains to provide water for fire protection and to serve fire hydrants is 6 inches. Larger mains are required if necessary to allow the required fire flow while maintaining a minimum residual pressure of 20 psi at ground level at all points in the distribution system.(6) FIRE PROTECTION. The minimum flow requirement for water mains serving fire hydrants is 500 gpm at 20 psi residual pressure at ground level at all points in the distribution system.(7) SMALL DIAMETER MAINS. Any departure from minimum requirements shall be justified by hydraulic analysis and future water use, and will be considered for approval by the department only in special circumstances. The main sizing for small diameter mains may be calculated based upon a fixture unit determination. Note: See the requirements of ch. SPS 382 for guidance in sizing mains according to fixture units to be served.
(8) DEAD ENDS. Dead ends shall be minimized by looping mains whenever possible. Where dead end mains occur, they shall terminate with a fire hydrant, if flow and pressure are sufficient, or with an approved flushing hydrant or blow-off for flushing purposes. Flushing devices shall be installed on the dead end of all water main stubs 20 feet or more in length unless a shut-off valve is installed near the point of connection and closed until the stub is placed in service in the future. Flushing devices shall be sized to provide a minimum velocity of 2.5 feet per second in the water main being flushed. Flushing devices on dead end mains shall be installed downstream of all services. No flushing device shall be directly connected to any sewer. Note: Refer to AWWA standard C651 for required flows and openings to flush pipelines.
(9) VALVING. Sufficient valves shall be provided on water mains so that inconvenience or sanitary hazard to water users will be minimized during maintenance and construction. Valves shall be located at not more than 800-foot intervals for distribution system mains. Valves shall not be located at more than 1-mile intervals for transmission mains and shall be located immediately on each side of a distribution system branch.(10) FRICTION COEFFICIENTS. Unless other values are specially approved by the department, the following maximum "C" values, using the Hazen-Williams formula, shall be used for checking the hydraulic characteristics of new water mains shown on plans and specifications submitted for review: - See PDF for table The "C" value of existing water mains and for all water mains with a pipe diameter of 12 inches or less may be less than the maximum "C" value for new pipe and shall be considered in distribution system analysis. The actual interior diameter of the pipe being modeled shall also be considered in the distribution system analysis.
Wis. Admin. Code Department of Natural Resources NR 811.70
CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.Amended by, CR 22-074: am. (1), (4), (9) Register January 2024 No. 817, eff. 2-1-24; correction in (1) made under s. 35.17, Stats., Register January 2024 No. 817, eff. 2/1/2024