Drafting From Low Pressure Hydrants
© 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

There are areas in the district where ridgeline hydrants are located at approximately the same level as reservoirs. In those instances there is insufficient lift to provide reasonable fire flows from those hydrants through conventional large diameter hose or soft suction hoses.

The example presented here is of the hydrant at 48 Tappan Lane, next to the Sleepy Hollow Reservoir. It is on an 8" main and is backed up by nearly 3 million gallons of storage, however the hydrant's static pressure is often 4 psi or less, depending on the level in the reservoir, and direct flows from the hydrant are often less than 200 GPM. In addition to determining fire flows, testing can uncover a number of mechanical problems from valves that don't operate properly to leaks and even pump damaging debris flowing from hydrants. It is imperative that we discover problems and get them repaired before the hydrant is needed in an emergency.

The Sta. 42 B-Shift "hydrant crew"
will show you how it's done

When drafting the primary consideration involves effectively positioning the apparatus. Hard suction hose is not easy to manipulate and on narrow roadways you may find yourself blocking access by other emergency vehicles or egress by citizens. At the 48 Tappan Lane location an engine with hard suction hose can back into the reservoir access road and draft using its front suction connection.

In this scenario another advantage of being next to the reservoir is the ability to determine the level of water in the reservoir. If there is enough head to purge the air out of the hard suction hose, the apparatus operator can vent much of the air using the front suction drain line prior to priming the pump and delivering water. Otherwise the same procedures as used for drafting out of a static source should be used.

The reservoir water level gauge

  PROCEDURE USING A TYPE 1 ENGINE

Spot the apparatus correctly

Use someone on the ground to help. Set up so that you can get a nice wide horseshoe bend in the hose. Someone who can see the hydrant should guide the driver and another person should watch the rear of the apparatus for safety.

Remove the 6" hard suction

Lay the hose out in a position close to where it will be utilized, female ends toward the apparatus. Also get out needed fittings and tools such as a LDH spanner, mallet, hydrant wrench and LDH double female adapter.

Remove the front soft suction

Uncouple the soft suction and remove the 6" to 4" reducer.

Hook one length to the hydrant

Connect the LDH double female to the hydrant. Connect the 6" to 4" reducer to the end of the hard suction hose. Couple the hose to the hydrant. This is done most efficiently using three personnel, two to level the hose while the third spins and tightens the coupling.

Hook the other length to the engine

Connect the second length to the front suction connection. Utilizing the full crew of three to level the hose makes the hookup go much faster and easier.

Hook the lengths together

With one person on each hose and a third person making the connection, level and connect the hoses and tighten with a mallet. (The reason for this order of connecting is that it is easier to make the final connection in a more open space.)

Prepare to pump

Open the hydrant fully. Purge the air from the line using the front suction drain. Once water is showing close the drain, make sure the tank to pump line is closed, expel remaining air with the primer and establish a prime using standard drafting procedures.

The engine should have no problem pumping at least 1000 GPM from his hookup.

  INDEX OF RELATED FEATURES

Drafting with a Tender-Engine (E642)

Drafting on Mulholland Ridge (Donald Drive)

Drafting at Canyon School Tank (Northern Railway)


Return to Water Supply Index

Back to Information Section


  Back

Legal Disclaimer

Unless otherwise noted, all contents of these WWW pages © 1996-2002, FireHydrant.org