Achieving Maximum Flow from Hydrants
Part Two; The Two Pumper Hookup
© 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

Two pumper hookups involve each engine taking one discharge outlet from the same hydrant for water supply. The engine most likely to require the greatest flow would hook to the steamer outlet and the other engine would take the 2½" outlet.

The two pumper hookup would be practical in locations where two separate engines could readily access the same hydrant.

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.

    (Attempts should be made not to obstruct access to the hydrant by a second engine.)

  2. The first arriving engine fulfills its tactical objectives.

  3. The second arriving engine takes a position and makes a LDH suction hookup to the 2½" hydrant outlet.

  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 compensating line should be connected to the pony suction connections of the two engines.

Trial Results:

The first arriving engine had no difficulty maintaining residual pressure. (It never dropped below 30 p.s.i.) The second arriving engine dropped below 10 p.s.i. residual pressure but this weakness would be adequately corrected by introducing the compensation 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.

Once pumping operations have started, a compensation line should always be connected between the auxilliary suction inlets of both engines. The concept here is to share intake supply, not mix intake and discharge connections. The excess residual intake pressure at one engine will seek balance with the lower intake pressure of the second engine.

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

First engine makes a steamer hookup
Normal flow evolutions take place
Second engine connects LDH suction to 2½
View of the 2-pumper hookup
2000 GPM combined flow

Continue to Dual Pumping

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