Pumping Apparatus Driver/
Operator — Lesson 8 Customary
Pumping Apparatus Driver/Operator
Handbook, 2nd Edition
Chapter 8 Customary — Theoretical
Pressure Calculations
Learning Objectives
1. Answer questions about friction loss,
elevation pressure, and total pressure loss
(TPL).
2. State the equation for determining friction
loss.
3. Calculate friction loss.
4. Select facts about determining your own
friction loss coefficients.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–1
Learning Objectives
5. Test hose carried on your apparatus to
determine friction loss.
6. Answer questions about appliance
pressure loss.
7. Select facts about elevation pressure.
8. State the equations for determining
elevation pressure.
Pumping Apparatus
Driver/Operator
8 Customary–2
(Continued)
Learning Objectives
9. Calculate elevation pressure.
10. Answer questions about hose layouts.
11. Calculate total pressure loss in single
hoseline layouts.
12. Calculate total pressure loss for wyed
hoselines of equal length.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–3
Learning Objectives
13. Calculate total pressure loss for siamesed
hoselines of equal length.
14. Calculate total pressure loss for standpipe
operations.
15. Calculate total pressure loss for multiple
hoselines of unequal length.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–4
Learning Objectives
16. Calculate total pressure loss for wyed
hoselines of unequal length and for
manifold hoselines.
17. Calculate total pressure loss for master
streams.
18. State the equation for determining pump
discharge pressure.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–5
Learning Objectives
19. Calculate pump discharge pressure.
20. State the equation for determining net
pump discharge pressure (NPDP).
21. Calculate net pump discharge pressure.
Pumping Apparatus
Driver/Operator
8 Customary–6
Friction Loss and
Elevation Pressure
• To produce effective fire streams, it is
necessary to know the amount of friction loss
in the fire hose and any pressure loss or gain
due to elevation.
• Causes of friction loss
–
–
–
–
Hose condition
Coupling condition
Kinks
Volume of water flowing per minute
Pumping Apparatus
Driver/Operator
8 Customary–7
(Continued)
Friction Loss and
Elevation Pressure
• The calculation of friction loss must take into
account the length and diameter of the
hoseline and any major hose appliances
attached to the line. Because the amount of
hose used between an engine and the nozzle
is not always the same, driver/operators must
be capable of determining friction loss in any
given length of hose.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–8
Friction Loss and
Elevation Pressure
• Elevation differences, such as hills, gullies,
aerial devices, or multistoried buildings,
create a pressure loss or gain known as
elevation pressure.
• Together, friction loss and elevation pressure
loss are referred to as total pressure loss.
Pumping Apparatus
Driver/Operator
8 Customary–9
Determining Friction Loss
• Equation A
FL = CQ2L
FL = Friction loss in psi
C = Friction loss coefficient (from Table 8.3)
Q = Flow rate in hundreds of gpm (flow/100)
L = Hose length in hundreds of feet (length/100)
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–10
Determining Friction Loss
• Step 1 — Obtain from Table 8.3 the friction
loss coefficient for the hose being used.
• Step 2 — Determine the number of hundreds
of gallons of water per minute flowing (Q)
through the hose by using the equation:
Q = gpm/100
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–11
Determining Friction Loss
• Step 3 — Determine the number of hundreds
of feet of hose (L) by using the equation:
L = feet/100
• Step 4 — Plug the numbers from Steps 1, 2,
and 3 into Equation A to determine the total
friction loss.
Pumping Apparatus
Driver/Operator
8 Customary–12
Determining Your Own
Friction Loss Coefficients
• If you wish to calculate more accurate results
for the fire hose that is carried on your
apparatus, rather than use the results from
the standard friction loss coefficients, it is
recommended that you test your hose to
determine the actual coefficients.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–13
Determining Your Own
Friction Loss Coefficients
• In order to get results indicative of averages
that can be expected on the fireground, it is
necessary to use the same hose that would
be used on the fireground.
• Conduct tests on hose that is in service, not
on hose that has been in storage or hose that
has never been put into service (unless new
hose is about to be placed into service).
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–14
Determining Your Own
Friction Loss Coefficients
• Departments should test only one hose type
at a time.
• It is important that all measuring devices are
in good condition and properly calibrated.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–15
Determining Your Own
Friction Loss Coefficients
• Needed equipment
– Pitot tube or flowmeter
– Two in-line gauges,
calibrated in increments
of 5 psi or less
– Hose to be tested
– Smoothbore nozzle (if
using pitot tube)
– Any type nozzle (if using
flowmeter)
Pumping Apparatus
Driver/Operator
8 Customary–16
(Continued)
Determining Your Own
Friction Loss Coefficients
• Refer to Skill Sheet 8-1 Customary for
detailed instructions.
Pumping Apparatus
Driver/Operator
8 Customary–17
Appliance Pressure Loss
• Appliances on the fireground include
reducers, increasers, gates, wyes, manifolds,
aerial apparatus, and standpipe systems.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–18
Appliance Pressure Loss
• Appliance friction loss is insignificant when
the total flow through appliances is less than
350 gpm.
• For this lesson, assume a 0 psi loss for flows
less than 350 gpm and a 10 psi loss for each
appliance (other than master stream devices)
in a hose assembly when flowing 350 gpm or
more.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–19
Appliance Pressure Loss
• Friction loss caused by handline nozzles is
not considered in the calculations in this
lesson, as it is generally insignificant in the
overall pressure in a hose assembly.
• For this lesson, assume a friction loss of 25
psi in all master stream appliances,
regardless of the flow.
Pumping Apparatus
Driver/Operator
8 Customary–20
Elevation Pressure
• Elevation pressure is created by elevation
differences between the nozzle and the
pump.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–21
Elevation Pressure
• Water exerts a pressure of 0.434 psi per foot
of elevation.
• When a nozzle is operating at an elevation
higher than the apparatus, this pressure is
exerted back against the pump.
• To compensate for this pressure “loss,”
elevation pressure must be added to friction
loss to determine total pressure loss.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–22
Elevation Pressure
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–23
Elevation Pressure
• Operating a nozzle lower than the pump
results in pressure pushing against the
nozzle.
• This “gain” in pressure is compensated for by
subtracting the elevation pressure from the
total friction loss.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–24
Elevation Pressure
Pumping Apparatus
Driver/Operator
8 Customary–25
Determining Elevation Pressure
• Equation B
EP = 0.5H
EP = Elevation pressure in psi
0.5 = A constant
H = Height in feet
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–26
Determining Elevation Pressure
• It is generally easier to determine elevation
pressure in a multistoried building by another
method. By counting the number of stories of
elevation, use:
• Equation C
EP = 5 psi x (number of stories – 1)
Pumping Apparatus
Driver/Operator
8 Customary–27
Hose Layouts
• The combination of friction loss and elevation
pressure is referred to as total pressure loss.
• Pressure changes are possible due to hose
friction loss, appliance friction loss (when
flows exceed 350 gpm), and any pressure
loss or gain due to elevation.
• By adding all the affecting pressure losses,
the total pressure loss can be determined for
any hose lay.
Pumping Apparatus
Driver/Operator
8 Customary–28
Simple Hose Layouts
• Single hoseline
• Multiple hoselines (equal length)
• Wyed hoselines (equal length)
• Siamesed hoselines (equal length)
Pumping Apparatus
Driver/Operator
8 Customary–29
Single Hoseline
• Is the most commonly used hose lay
• Presents the simplest friction loss calculations
Pumping Apparatus
Driver/Operator
8 Customary–30
Multiple Hoselines (Equal Length)
• When determining the friction loss in equal
length multiple lines whose diameters are the
same, it is only necessary to perform
calculations for one line.
• When the diameters of the hoselines vary,
friction loss calculations must be made for
each hoseline. The pump discharge pressure
is then set for the highest pressure.
Pumping Apparatus
Driver/Operator
8 Customary–31
Wyed Hoselines (Equal Length)
• When using a wye, it is important that the
attack lines wyed from the supply line are the
same length and diameter in order to avoid
two different nozzle pressures and an
exceptionally difficult friction loss problem.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–32
Wyed Hoselines (Equal Length)
• When the nozzle pressure, hose length, and
diameter are the same on each wyed line, an
equal split of the total water flowing occurs at
the wye appliance.
• This enables only one of the wyed hoselines
to be considered when computing the total
pressure lost.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–33
Wyed Hoselines (Equal Length)
• Step 1 — Compute the number of hundreds
of gpm flowing in each wyed hoselines by
using the equation:
Q = flow rate (gpm)
100
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–34
Wyed Hoselines (Equal Length)
• Step 2 — Determine the friction loss in one of
the wyed attack lines using the equation:
FL = CQ2L
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–35
Wyed Hoselines (Equal Length)
• Step 3 — Compute the total number of
hundreds of gpm flowing through the supply
line to the wye by using the following
equation:
QTotal = (gpm in attack line 1) + (gpm in attack line 2)
100
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–36
Wyed Hoselines (Equal Length)
• Step 4 — Determine the friction loss in the
supply line using Equation A:
FL = (C)(QTotal)2(L)
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–37
Wyed Hoselines (Equal Length)
• Step 5 — Add the friction loss from the supply
line, one of the attack lines, 10 psi for the wye
appliance (if the total flow exceeds 350 gpm)
and elevation pressure (if applicable) to
determine the total pressure loss.
Pumping Apparatus
Driver/Operator
8 Customary–38
Siamesed Hoselines
(Equal Length)
• The easiest method is to use Equation A.
When calculating friction loss in siamesed
lines, however, it is necessary to use a
different set of coefficients than for single
hoselines.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–39
Siamesed Hoselines
(Equal Length)
• Step 1 — Compute the total number of
hundreds of gpm flowing by using the
equation:
Q = gpm flowing
100
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–40
Siamesed Hoselines
(Equal Length)
• Step 2 — Determine the friction loss in the
attack line by using Equation A (FL = CQ2L).
Use Table 8.3 for the coefficient in this step.
• Step 3 — Determine the amount of friction
loss in the siamesed lines using Equation A
(FL = CQ2L). Use Table 8.4 to obtain the
coefficient in this step.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–41
Siamesed Hoselines
(Equal Length)
• Step 4 — Add the friction loss from the
siamesed lines, attack line, 10 psi for the
siamese appliance (if flow is greater than 350
gpm), and elevation pressure (if applicable) to
determine the total pressure loss.
Pumping Apparatus
Driver/Operator
8 Customary–42
Complex Hose Layouts
• Standpipe operations
• Multiple hoselines (unequal length)
• Wyed hoselines (unequal length) and
manifold hoselines
• Master streams
Pumping Apparatus
Driver/Operator
8 Customary–43
Standpipe Operations
• In most cases, fire departments have
predetermined pressures that
driver/operators are expected to pump into
the fire department connection (FDC) of a
standpipe system.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–44
Standpipe Operations
• These pressures are
contained in the
department’s SOPs,
in the pre-incident
plan for that
particular property,
or on a faceplate
adjacent to the FDC.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–45
Standpipe Operations
• In order to be able to determine the required
pressure for the standpipe system, it is
necessary to determine the total pressure
loss.
• Treat the FDC like any other hose appliance.
Pumping Apparatus
Driver/Operator
8 Customary–46
Multiple Hoselines
(Unequal Length)
• When unequal length hoselines are used, the
amount of friction loss varies in each line.
• For this reason, friction loss must be
calculated in each hoseline.
Pumping Apparatus
Driver/Operator
8 Customary–47
Wyed Hoselines (Unequal
Length) and Manifold Hoselines
• Remember that when hose lengths are
unequal in length and/or diameter, the total
pressure loss in the system is based on the
highest pressure loss in any of the lines.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–48
Wyed Hoselines (Unequal
Length) and Manifold Hoselines
• Step 1 — Compute the number of hundreds
of gpm flowing in each of the wyed hoselines
by using the following equation:
Q = discharge gpm
100
• Step 2 — Determine the friction loss in each
of the wyed lines using Equation A
(FL = CQ2L).
Pumping Apparatus
Driver/Operator
8 Customary–49
(Continued)
Wyed Hoselines (Unequal
Length) and Manifold Hoselines
• Step 3 — Compute the total number of
hundreds of gpm flowing in the supply line to
the wye or manifold by adding the sum of the
flows in the attack lines and dividing by 100.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–50
Wyed Hoselines (Unequal
Length) and Manifold Hoselines
• Step 4 — Determine the friction loss in the
supply line using the equation:
FL = (C)(QTotal)2(L)
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–51
Wyed Hoselines (Unequal
Length) and Manifold Hoselines
• Step 5 — Add the friction loss from the supply
line, the wye or manifold appliance (if total
flow is greater than 350 gpm), elevation loss,
and the wyed line with the greatest amount of
friction loss to determine the total pressure
loss.
Pumping Apparatus
Driver/Operator
8 Customary–52
Master Streams
• Remember to add a 25 psi pressure loss to
all calculations involving master stream
devices.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–53
Master Streams
• Determining friction loss for master streams is
essentially the same as those used for other
fire streams, unless unequal length or
diameter hoselines are used to supply a
master stream appliance.
• In this situation, use an average of the hose
lengths for ease of calculation.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–54
Master Streams
• Aerial devices with piped waterways are
treated in the same manner as master stream
appliances: using a friction loss of 25 psi to
include the intake, internal piping and nozzle.
Pumping Apparatus
Driver/Operator
8 Customary–55
Determining Pump
Discharge Pressure
• In order to deliver the necessary water flow to
the fire location, the pump discharge pressure
at the apparatus must be enough to
overcome the sum of all pressure losses.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–56
Determining Pump
Discharge Pressure
• Equation D
PDP = NP + TPL
PDP = Pump discharge pressure in psi
NP = Nozzle pressure in psi
TPL = Total pressure loss in psi (appliance,
friction, and elevation losses)
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–57
Determining Pump
Discharge Pressure
• It is often important that attack lines be
supplied with water at somewhere near the
required nozzle pressure until the
driver/operator has time to calculate the
correct pump discharge pressure.
• It is SOP in many departments to initially
charge attack lines with fog nozzles at 100 psi
and solid stream nozzles at 50 psi while
setting up for the pump operation.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–58
Determining Pump
Discharge Pressure
• Supplying multiple, wyed, or manifold
hoselines requires different pump discharge
pressures for each attack line.
• Because this is not possible, set the pump
discharge pressure for the hoselines with the
greatest pressure demand.
–
–
–
–
Solid stream nozzle (handline) — 50 psi
Solid stream nozzle (master stream) — 80 psi
Standard fog nozzle — 100 psi
Low-pressure fog nozzle — 50 psi or 75 psi
Pumping Apparatus
Driver/Operator
8 Customary–59
Determining Net Pump
Discharge Pressure
• Centrifugal pumps are able to take advantage
of incoming water pressure into the pump.
• Thus, if a pumper is required to discharge
150 psi, and it has an intake pressure of 50
psi coming into the pump, the pump only
needs to add 100 psi more to meet the
demand. This concept is called net pump
discharge pressure (NPDP).
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–60
Determining Net Pump
Discharge Pressure
• NPDP takes into account all factors that
contribute to the amount of work the pump
must do to produce a fire stream.
• When a pumper is being supplied by a
hydrant or a supply line from another pumper,
the NPDP is the difference between the pump
discharge pressure and the incoming
pressure from the hydrant.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–61
Determining Net Pump
Discharge Pressure
• Equation E
NPDPPPS = PDP – Intake reading
NPDPPPS = Net pump discharge pressure
from a positive pressure source
PDP = Pump discharge pressure
Note: This equation does not apply to
situations where the pumper is operating at a
draft.
Pumping Apparatus
Driver/Operator
8 Customary–62
Summary
• To fulfill the primary fireground function of
supplying attack crews with an adequate
volume of water at pressures that are both
safe and effective, driver/operators must be
able to make certain hydraulic calculations in
the field.
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–63
Summary
• To do this, they must know how to factor in
losses in pressure due to friction, as well as
pressure losses or gains because of elevation
differences.
• In addition, driver/operators must be able to
calculate pump pressure required to supply
multiple hoselines of varying diameters,
lengths, and configurations.
Pumping Apparatus
Driver/Operator
8 Customary–64
Discussion Questions
1. What four things can cause friction loss?
2. What is total pressure loss (TPL)?
3. What is the equation for determining friction
loss?
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–65
Discussion Questions
4. What are the equations for determining
elevation pressure?
5. What are the four types of simple hose
layouts?
6. What are the four types of complex hose
layouts?
(Continued)
Pumping Apparatus
Driver/Operator
8 Customary–66
Discussion Questions
7. What is the equation for determining pump
discharge pressure?
8. What is the equation for determining net
pump discharge pressure (NPDP)?
Pumping Apparatus
Driver/Operator
8 Customary–67