Wisconsin Administrative Code › Department of Natural Resources › NR 800 - Environmental Protection - Water Supply › Chapter NR 811 - Requirements For The Operation And Design Of Community Water Systems › Subchapter X - Distribution Systems › Section NR 811.70 - Water main design

Current through June 24, 2024
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.