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Understanding the theoretical and practical application of hydraulics essential for pump operation. The study of fire ground hydraulics is divided into two categories, theoretical and rule of thumb.
The driver/operator must be able to apply both.

Nozzle Loss
Attack Line Loss
Elevation Loss
Manifold/ Appliance
Standpipe Loss
Supply Line Loss

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NP - Nozzle Pressure
FL Friction Loss
AL Appliance Loss
EL Elevation Pressure
TPL - Total Pressure Loss
NPDP - Net Pump Discharge Pressure

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In the classroom and non-emergency activities of the fire department, mathematical equations are used to calculate the flow characteristics of our equipment and systems. This method of calculation is commonly referred to as
“Theoretical Hydraulics”. By using mathematical formulas, a relatively accurate calculation of the total probable friction loss is obtained. This method is normally more accurate than Rule of
Thumb.

There are many formulas and methods for figuring friction loss but the Renton Fire
Department has adopted the following for use in its training program.
FL = CQ 2 L
Where
Q = Quantity
C = Coefficient
L = Length in 100’s

Coefficients for Renton Fire Department hose:
1 ¾ “
2 ½ “
3 ½ “
5 “
C = 15.5
C = 2
C = 0.34
C = 0.08

Two 2 ½” 0.5
Three 2 ½” 0.22

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On the fire ground, the driver/operator normally works with a condensed and simplified application known as “Rule of
Thumb Hydraulics”. Rule of thumb hydraulic formulas are a chosen series of fixed, rounded values that can be applied to an operation sequentially to build a water delivery system.

Fixed Rounded Value Examples
2 ½” Combination Nozzle 250 GPM
1 ¾” Combination Nozzle 125 GPM
1 ¾” Hose 25 psi FL / Section
2 ½” Hose 06 psi FL / Section
Master Stream Devices 25 psi FL
Appliances (Wye etc…)
Appliances (Wye etc…)
Elevation
0 FL @ <350 gpm
10 psi FL @ > 350 gpm
05 psi FL / Floor

< 350 gpm no calculated loss
> 350 gpm 10 psi per appliance
25 psi for all master stream devices
25 psi for all standpipes

Types of Nozzles
Solid Stream
Broken Stream
Periphery Deflected
(Combination )
Impinging stream
(Naval type)

The purpose of any nozzle is to provide a restriction of the flow to build pressure. This restriction, and subsequent created pressure, provides a usable velocity to project the water stream. For any one flow, there is one correct nozzle size (restriction) to develop the optimum pressure and velocity.
Restriction

Smooth Bore Nozzle - Hand line - 50 PSI
½” thru 1 ¼” nozzles
Smooth Bore Nozzle - Master Stream - 80 PSI nozzles 1 ¼” and over
Fog Nozzle - 100 PSI all nozzles

The mechanical characteristics of a solid stream nozzle produce a compact stream that has a higher mass and velocity. These features typically yield better reach and penetration.

The interior diameter of the nozzle is gradually decreased until it reaches a point just short of the outlet. At this point the straight cylindrical bore has a length from 1 to 1 ½ times its bore, this area is known as the stream shaper

Water flowing through a nozzle is subject to the same physical principals of friction as hose. The net effect of friction in a solid stream nozzle is the creation of a laminar flow. The center of the flowing stream is faster than the edge. This creates a peripheral turbulence that is visible after the stream exits the nozzle.

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Discharge Volume:
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29.7 x D 2 x NP
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Nozzle Reaction:
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1.57 x D 2 x NP

A stream of water remains in a solid mass, not losing continuity until it strikes an object, is overcome by gravity or is changed by friction with the air. Fog stream nozzles are designed around this theory and are commonly called broken stream appliances

All fog streams are of two mechanical types, Periphery-deflected or impinging stream. The shape and reach of a fog stream are results of the appliance shape and the velocity/pressure of the water.

Impinging Stream fog patterns are produced by driving jets of water together at a set angle to break the streams into finely divided particles. These appliances generally produce wide angle fog patterns.

Periphery –Deflected streams are produced by deflecting water from the periphery of an inside circular stem to the inner circumference of the adjustable barrel. The position of the barrel varies the shape of the stream from a light fog to a straight stream.
There are two common types of these nozzles, automatic and non-automatic.

Automatic
Automatic Periphery-Deflected nozzles have a spring loaded baffle assembly that reacts to incoming pressure. The baffle is calibrated to function at 100 PSI.
The model illustrated has a sliding valve which allow the firefighter to meter the flow at the nozzle.

Automatic
When pressure at the nozzle is less, the baffle moves in to maintain the pattern. When the pressure is greater than
100 PSI the baffle moves out to allow more volume and minimize the nozzle reaction.

Automatic
Task Force Tip nozzles have a slide valve assembly that allows the water flow at the tip to be metered. By using this valve design, the nozzle has a smoother flow and less turbulence. Note the valve position in the illustrations.

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Nozzle Reaction:
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0.0505 x Q x NP

Slide Valve
Gated ½ Way

Ball Valve
Gated ½ Way

Nozzle reaction is the force that a firefighter feels when he is operating a nozzle. Nozzle reaction is primarily a result of discharge pressure at the nozzle. If the nozzle pressure is lowered, the firefighter will note a corresponding decrease in the nozzle reaction.

To calculate the nozzle reaction use the following formulas, note same flows can often be developed at a far lower nozzle reaction in solid stream nozzles. Traditional thought is that solid bore hand lines should be pumped at 50 psi. Any nozzle pressures higher than 65 psi becomes unmanageable. In the following table review and compare the reaction force of various fire streams.
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Nozzle Reaction: Solid Stream
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1.57 x D 2 x NP
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Nozzle Reaction: Fog Stream

0.0505 x Q x NP

Handline Nozzle Reaction Chart
125 GPM
3/4” tip @ 56 NP combination @ 100 NP
150 GPM
7/8” tip @ 44 NP combination @ 100 NP
175 GPM
200 GPM
7/8” tip @ 60 NP combination @ 100 NP
250 GPM
1” tip @ 46 NP combination @ 75 NP combination @ 100 NP
300 GPM
1” tip @ 72 NP
1-1/8” tip @ 50 NP combination @ 100 NP
325 GPM
1” tip @ 100 NP
1-1/8” @ 64 NP combination @ 100 NP
1” tip @ 120 NP
1-1/8” tip @ 75 NP
1-1/4” tip @ 50 NP combination @ 100 NP
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
49 NR
63 NR
53 NR
76 NR
72 NR
88 NR
72 NR
87 NR
101 NR
113 NR
99 NR
126 NR
157 NR
127 NR
152 NR
188 NR
149 NR
123 NR
164 NR

FL = CQ 2 L
Where
Q = Quantity
C = Coefficient
L = Length in 100’s

Coefficients for Renton Fire Department hose:
1 ¾ “
2 ½ “
3 ½ “
5 “
C = 15.5
C = 2
C = 0.34
C = 0.08

Two 2 ½” 0.5
Three 2 ½” 0.22

2 ½” – 400 ‘
1 ¾” – 150’
1 ¾” – 200’
125 gpm
125 gpm

Answer
100 psi NP
48 psi FL 1 ¾”, 200’
50 psi FL 2 ½”, 400’
198 psi NPDP
(36 psi FL 1 ¾”, 150’ plus 5 psi elevation is less than 200’. Pump to the highest friction loss)

200’ of 5”
200’ 1 ¾”
200’ 2 ½”
200 gpm
250 gpm

Answer
100 psi NP
5 psi elevation
124 psi 1 ¾”, 200’
10 psi appliance loss (>350gpm)
3.24 psi 5”, 200’
242.24
psi NPDP
(2 ½” FL is 25 psi, pump to the highest loss)

2 ea. 2 ½” 50’
600 GPM
1 ½” tip
200’ of 5”
2 ½” 200’
250 GPM

Answer
100 psi NP
25 psi FL, 2 ½”
10 psi AL
11.56 psi FL 5”
146.56
psi NPDP
(NP 80 psi, 1 ½” tip 600 gpm / 25 psi FL
Masterstream / 9 psi FL 2 ½” Siamese
= 114 psi. Pump to the highest loss. Gate down the Master stream if necessary)

1 ¼”
Solid Bore
1 ¾” 150’
200 gpm
250’ 2 ½’
125 gpm
1 ¾” 200’
2 ½’” 200’
250 gpm

100 psi NP
Answer
2 ½” 25 psi FL
1 ¾” 200 gpm, 93 psi FL
1 ¾” 125 gpm, 48.4 psi FL
50 psi
2 ½” with 1 ¼” 328 gpm, 53.7 psi
193 psi NPDP, pump to the highest friction loss

150 gpm
200’ 1 ¾”
40’

Answer
100 psi NP
17.36 psi EL (.434/ft)
69.75 psi FL
187.11
psi NPDP

100” Siamesed 2 ½”
200’ 1 ¾” 150 gpm

Answer
100 psi NP @ 150 gpm
69.75 psi FL 1 ¾”, 200’
34.72 psi EL (.
434 psi X 8 floors above the 1 st )
25 psi FL Standpipe
01.125 psi FL Siamesed 2 ½”
230.59 psi NPDP

100’ of 2 ½”
200’ of 1 ¾” @ 200 gpm

Answer
100 psi NP @ 150 gpm
124 psi FL 1 ¾”, 200’
34.72 psi EL (.434 psi X 8 floors above the 1 st )
25 psi FL Standpipe
08 psi FL Siamesed 2 ½”
291.72 psi NPDP
What single adjustment could you make to cut the friction loss by NPDP by 25 psi?

2 ea. / 100’ of 2 ½”
150’ of 2 ½”
250 GPM
150’ of 2 ½”
150’ of 1 ¾”
180 GPM

Answer
100 psi NP @ 180 gpm
75.33 psi FL 1 ¾”, 150’
9.72 psi FL – 2 ½”, 150’
26.04 psi EL (.434 psi X 6 floors above the 1 st )
25 psi FL Standpipe
09.25 psi FL Siamesed 2 ½”
245 psi NPDP
The 2 ½” NPDP was 187.72 pump to the highest friction loss.
How would the excess pressure be dealt with in this line?