Water Mains

The size of the main will limit the amount of water that can be efficiently delivered. For main sizing, Chapter NR 811 Subpart XI, W.A.C. requires the following:

• The minimum diameter pipe to provide water for fire protection and supply hydrants is six inches
• The minimum flow required for water mains supplying hydrants is 500 gpm at 20 psi residual pressure
• Ground level pressure of all points in the system and under all flow conditions is 20 psi
• Normal static pressure is between 35 psi and 100 psi