R309-550-5. Water Main Design

  (1) Distribution System Pressure.

  (a) The distribution system shall be designed to maintain minimum pressures as required in R309-105-9 at points of connection, under all conditions of flow.

  (b) When static pressure exceeds 150 psi in new distribution water lines, pressure reducing devices shall be provided on mains in the distribution system where service connections exist.

  (2) Design Flow Rates.

  Flow rates used when designing or analyzing distribution systems shall meet the minimum requirements in R309-510.

  (3) Hydraulic Analysis.

  (a) All water mains shall be sized following a hydraulic analysis based on flow demands and pressure requirements.

  (b) Where improvements will upgrade more than 50% of an existing distribution system, or where a new distribution system is proposed, a hydraulic analysis of the entire system shall be prepared and submitted for review prior to plan approval.

  (c) Some projects require a hydraulic model. The Division may require submission of a hydraulic modeling report and/or certification, as outlined in R309-511, prior to plan approval.

  (4) Minimum Water Main Size.

  For water mains not connected to fire hydrants, the minimum line size shall be 4 inches in diameter, unless they serve picnic sites, parks, semi-developed camps, primitive camps, or roadway rest-stops. Minimum water main size, serving a fire hydrant lateral, shall be 8 inches in diameter unless a hydraulic analysis indicates that required flow and pressures can be maintained by 6-inch lines.

  (5) Fire Protection.

  When a public water system is required to provide water for fire flow by the local fire code official, or if the system has installed fire hydrants on existing distribution mains for that purpose:

  (a) The design of the distribution system shall be consistent with the fire flow requirements as determined by the local fire code official.

  (b) The location of fire hydrants shall be consistent with the requirements of the State-adopted fire code and as determined by the local fire code official.

  (c) The pipe network design shall permit fire flows to be met at representative locations while minimum pressures, as required in R309-105-9, are maintained at all times and at all points in the distribution system.

  (d) Fire hydrant laterals shall be a minimum of 6 inches in diameter.

  (6) Geologic Considerations.

  The character of the soil through which water mains are to be laid shall be considered. Special design and burial techniques shall be employed for Community Water Systems in areas of geologic hazard (e.g., slide zones, fault zones, river crossings, etc.)

  (7) Dead Ends.

  (a) To provide increased reliability of service and reduce head loss, dead ends shall be minimized by making appropriate tie-ins whenever practical.

  (b) Where dead-end mains occur, they shall be provided 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 sized to provide flows that will give a velocity of at least 2.5 fps in the water main being flushed. No flushing device shall be directly connected to a sewer.

  (8) Isolation Valves.

  Sufficient number of valves shall be provided on water mains so that inconvenience and sanitary hazards will be minimized during repairs. Valves shall be located at not more than 500 foot intervals in commercial districts and at not more than one block or 800 foot intervals in other districts. Where systems serve widely scattered customers and where future development is not expected, the valve spacing shall not exceed one mile.

  (9) Corrosive Soils and Waters.

  Consideration shall be given to the materials to be used when corrosive soils or waters will be encountered.

  (10) Special Precautions in Areas of Contamination.

  Where distribution systems are installed in areas of contamination:

  (a) pipe and joint materials which are not susceptible to contamination, such as permeation by organic compounds, shall be used; and,

  (b) non-permeable materials shall be used for all portions of the system including water mains, service connections, and hydrant leads.

  (11) Water Mains and Other Sources of Contamination.

  Caution shall be exercised when locating water mains at or near certain sites such as sewage treatment plants or industrial complexes. Individual septic tanks shall be located and avoided. The Division shall be contacted to establish specific design requirements prior to locating water mains near a source of contamination.