Pressurized Dry Hydrant Systems
© 2001 Capt. Willis Lamm, Water Supply Officer, Moraga-Orinda (CA) Fire District

  INTRODUCTION

In locations where homes are located higher than water distribution zones, fire department supplied "dry" hydrant systems are necessary to provide water for fire fighting. These systems require an engine to pump into a fire department connection (FDC) that supplies one or more "dry" hydrants located in the higher elevations.

Streets within MOFD where dry hydrant systems are the only viable source of water include:

  • Knickerbocker Ln.

  • Nobi Ln.

  • Sunnyside Ln.

  DESIGN OBJECTIVES

The dry hydrant system should be designed so that a minimum of 1000 GPM can be delivered to the fireground with a minimum amount of confusion and delay and within normal pump operating pressures. The FDC should be readily discernible and accessible and the dry hydrants should be of conventional design but marked so that engine companies will know that they are not normal service hydrants.

In the Moraga-Orinda Fire District "special service" hydrants have red bodies to indicate to companies that a special operation has to take place in order to use these hydrants. District maps will indicate whether a specific evolution is required.

  OPERATIONAL FEATURES

  • All discharge hydrants shall be "pumper" style, Model 64 or equal.

  • All piping shall be rated at for a working pressure equal to the pressure required to sustain 1000 GPM from the engine pumping at the scene, but not less than 150 p.s.i., and be capable of withstanding static tests of two times the working pressure.

  • Older intakes are conventional FDC design with dual 2½" female swivels.
Standard FDC
  • Since the district adopted the LDH standard, newer intakes are pumper hydrants clearly marked as FDCs. Typically we use older hydrants which were taken out of service but which are still functional.
            Hydrant used as FDC
(Designing the system to work with LDH versus multiple 2½" lines provides several advantages such as eliminating most friction loss from the layout, reducing necessary relay operating pressures and eliminating large pressure swings between static and full flow operations.)

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DRY HYDRANT EVOLUTIONS

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