Achieving Maximum Flow from Hydrants
Part Three; Dual Pumping
© 2001 Capt. Willis Lamm, Water Supply Officer, Moraga-Orinda (CA) Fire District

The following procedures are examples of low water pressure evolutions based on the procedures of the Moraga-Orinda Fire District, presented for illustrative purposes.
  INTRODUCTION

With dual pumping, the first engine connects directly to a strong hydrant and the second engine connects directly to an unused LDH suction connection on the first engine.

The two pumper hookup would be practical in locations where two separate engines could not readily access the same hydrant, but could be positioned side by side.

For these trials we established water supply and flowed 1000 GPM from each engine through straight tips on engine deck pipes.

  THE EVOLUTION

  1. The first arriving engine makes a standard steamer hookup to the hydrant.

  2. The first arriving engine fulfills its tactical objectives.

  3. The second arriving engine takes a position and makes a LDH suction hookup to a LDH suction connection on the first engine.

    (The first engine's suction piping acts as a manifold and all water not taken by the first engine's pump is available to the second engine at hydrant pressure.)

  4. The second arriving engine fulfills its tactical objectives.

  5. If the residual pressure coming in to the second engine falls off too sharply (approaches or drops below 10 p.s.i.) a second supply line should be connected from the hydrant's 2½" outlet to a gated LDH or pony suction connection on the second engine.

    (Where practical, a 50 ft. section of LDH can be used to provide the second line and will have greater hydraulic efficiency.)

Trial Results:

The first arriving engine had no difficulty maintaining residual pressure. The second arriving engine dropped below 10 p.s.i. residual pressure but this weakness would be adequately corrected by adding the second hydrant supply line.

Key Points:

It would be a rare occurrence for two engines to each flow 1000 GPM during a two pumper hookup, however we know that it can be done.

A backup hydrant supply line should be connected beweeen an unused hydrant outlet to the second engine.

Engineers should communicate with each other when significant flow changes take place.

First engine makes a steamer hookup
Second engine hooks to LDH suction on first
View of the dual pumping operation
2000 GPM combined flow

Two Pumper Hookup

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