Drafting From Low Pressure Hydrants
Part Four
© 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.

This is a ridgeline of high elevation. The one hydrant in the area is connected to an 8 inch main. It has an average static pressure of only 8 psi with an available flow at normal head pressure of about 500 GPM. However by using hard suction, flows of about 1250 GPM can be obtained.

  GETTING EFFECTIVE WATER SUPPLY

A logical operation to fight a fire involving the ridgeline homes would be as follows:
  • First in engine does size-up and attacks the fire from the booster tank.

  • First arriving engine equipped with hard suction hose lays from the fire and makes a hard suction hookup to the hydrant.

  • Relay pressure should be 150 psi if using a dual lay of 2½" hose, or 100 psi if supplying LDH.

The hydrant in this location is set back from the roadway edge so the engine needs to be spotted against the curb and almost to the hydrant for a front suction hookup.

An appropriate sequence of actions is:

  1. Remove the hard suction hose and 4½" double female adapter from the engine.

  2. Remove the front soft suction and 6"x4½" reducer.

  3. Attach one length of hard suction to the front suction connection.

  4. Attach the double female adapter to the hydrant.

  5. Attach the 6" x 4½" reducer to the second length of hard suction and connect it to the hydrant.

  6. The reason we connect the two pieces of hard suction last is in the event the engine has to be repositioned to make the hookup, one person can hold the hose while the engine is moved.

  7. The front suction drain can be opened to purge air from the hose and hydrant pressure should be sufficient to purge remaining air from the system running the pump at moderate idle speed.
Hose laid out, attached to engine
Gender changer on the hydrant

Making the hydrant connection
Attaching the two sections together last
and tightening the lugs

From this hookup about 1250 GPM can be delivered.

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