HomeMy WebLinkAbout403.003B - Fire Hydrant Flow Testing
FIRE PREVENTION MANUAL
DEVELOPMENT REQUIREMENTS
403.003b FIRE HYDRANT FLOW TESTING
EFFECTIVE: MAY 2019
Current Revision Date: 5/21/19 Next Revision Date: 5/21/22
Author’s Name/Rank:
Byron Beagles
Fire Prevention Engineer Review Level: 1
Administrative Support:
Sherrie L. Badertscher
Management Analyst II
Section 403.003(b)
Page 1 of 7
PURPOSE
This policy has been established to provide direction to Fresno Fire Department
(FFD or Department) Prevention Division staff on conducting and documenting a
measured fire hydrant flow test for determining available water supply for fire
protection within the City of Fresno (City) and contract service areas.
APPLICATION
This policy applies to areas within the City and contract service areas that have
water supply systems capable of providing service to fire hydrants and fire sprinkler
systems. These systems are managed by several water purveyors in the
metropolitan Fresno area including the City of Fresno Water Division, Bakman Water
Company, Pinedale County Water District, and the Malaga County Water District.
There are also a limited number of private water systems not connected to the
aforementioned water purveyors that are capable of providing a fire protection water
supply including the Gallo Winery at 5610 E. Olive, and a large grocery products
distribution warehouse facility at 2797 S. Orange Ave. Both facilities were
developed in the County and fire protection is based on industrial fire insurance
standards.
OPERATIONAL POLICY
Measured flow testing will generally be done under the field supervision of the fire
prevention engineer with assistance from one or more fire inspectors. For private
fire hydrants, testing can be conducted by a licensed contractor for insurance
purposes but the results of such testing will not be used for fire protection system
design unless approved by the fire prevention engineer. Water purveyors are also
allowed to conduct flow testing on their own water system, but typically such testing
is deferred to the Department.
Section 403.003(b)
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Look up the flow test location on the GIS I-View water main/fire hydrant layers and
determine the best location for the test; considerations include avoiding high traffic
areas and flowing at a location near the project area where the water main
infrastructure is similar to the project frontage. Print the flow test area image for field
use and after test documentation.
If a high traffic volume area cannot be avoided, arrange through the battalion chief
the assistance of a fire company for traffic control. The Streets Maintenance
Division of Public Works can also be contacted to temporarily reprogram adjacent
traffic lights to flashing red if field conditions dictate. When either of these two
options is needed, be sure to time the flow test set-up so that you are ready when
assistance arrives in order to minimize their time away from normal duties. If time is
available, visit the test site on a previous day to verif y test hydrants are operational
and there is not adjacent street construction that could be impacted by water flow.
The following equipment is needed to conduct a fire hydrant flow test:
Portable radios
Base pad and hydrant barrel located operating valve hydrant wrenches
4-1/2 inch Hose Monster Big Boy diffuser with 0-60 psi liquid filled pressure
gauge and remote reading hose
Five (5’) foot length of large diameter fire hose (LDH) for attaching the Hose
Monster to the hydrant
Hose Monster Big Boy chart for pitot velocity pressure reading conversion to
gallons per minute
Calibrated liquid filled 0-100 psi static/residual pressure test gauge
2-1/2” outlet hydrant cap adapted for the static/residual gauge
Traffic cones
Reflective safety vest
Tool box with adjustable wrenches, assorted pliers/screw drivers, and small
plumbing parts (including hose bib adaptor, various reducers to ¼” pipe
thread, and a roll of Teflon tape)
Optional equipment:
Extra set of hydrant wrenches
Section 403.003(b)
Page 3 of 7
Turnout boots
Shovel
Bolt cutters
25 foot and 50 foot lengths of LDH
For multiple simultaneous hydrant flow testing, use additional conventional 4”
flow tube and pitot tube with liquid filled gauge. Use velocity pressure
conversion table and orifice co-efficient factors from National Fire Protection
Association (NFPA) 291, Recommended Practice for Fire Flow Testing and
Marking of Hydrants, for determining flow gpm from conventional flow testing
devices.
OPERATIONAL GUIDELINE
NFPA 291, Recommended Practice for Fire Flow Testing and Marking of Hydrants,
may be used for background information on conducting flow tests. Due to water
conservation issues and the logistics of multiple simultaneous fire hydrant flow tests ,
dropping residual pressures to 10 psi below static often is not always possible. This
pressure drop guideline is used in an attempt to get adjacent water well pumps to
start and requires an extended flow of water. For most fire sprinkler designs, the
required flow for the hydraulic design is much less than the minimum hydrant fire
flow requirement of 1500 gallons per minute (GPM) and the nearby well pumps may
not detect the fire sprinkler demand. It should also be noted that during the periodic
local ISO surveys, fire hydrant flow testing has always been conducted by using a
single hydrant.
Step-by-Step operations for conducting a flow test:
1. Locate the pre-determined flow hydrant and verify it is operational. Remove
the 4-1/2” cap and tighten the 2-1/2 inch caps.
Note: Know where the water is going to flow to! Verify that no open
construction trenches or other conditions will be impacted by the fire
flow. The flow diffuser will direct water laterally parallel to the street
but large flows may cause water to pond in traffic lanes. Take special
care in areas without curb and gutter.
2. Set up traffic cones and obtain traffic control assistance as needed for a
particular site.
Section 403.003(b)
Page 4 of 7
3. Attach the five (5’) foot length of LDH to the flow hydrant and connect the
diffuser which will lie in the gutter at most locations. Connect the remote
pressure reading tubing and velocity pressure gauge to the diffuser quick
connect coupling.
4. The static and residual pressure (S/R) gauge location needs to be upstream
from a flow fire hydrant on a dead end main or for circulating mains, located
as close as possible to the project site.
5. The S/R gauge may be placed at one of the following water sources:
a. On the 2-1/2” outlet using the cap adaptor on the closest fire hydrant to
the flow hydrant on the same water main. The hydrant with the S/R gauge
only needs to be opened a couple of turns to obtain a pressure reading.
b. On the supply (City) side of a reduced pressure (RP) backflow device
using one of the pipe adaptors in the tool kit. RP devices have arrows on
the body indicating direction of flow if not readily apparent from the water
meter location. There must be no domestic water use occurring on the
system side of the RP during the test. Choose the irrigation service RP if
possible (can be determined from the I-View water plat information layer)
as landscape watering is not permitted during the day.
c. On the hose bib of an adjacent house (ask permission!) using the adapto r
in the tool kit. There is no RP backflow device required for houses; just
verify that no water is being used while the test is being conducted. Never
place the S/R gauge downstream of an RP backflow device.
6. Position one (1) staff member at each of the two gauge locations described in
#4 and #6; establish communications via hand signals, portable radio, or cell
phone. Have pen and paper handy for recording gauge readings.
7. Upon notification from flow hydrant staff, record the static pressure at the S/R
hydrant. Standby to record the residual pressure upon notification from the
flow hydrant.
8. Fire dispatch should be notified of the flow test location and estimated
duration of the test. Opening and closing a flow hydrant may result in water
surges that can activate water flow switches on nearby fire sprinkler systems
and flooding of streets may result in citizen 911 calls.
9. Fully open the flow hydrant slowly and adjust the Hose Monster LDH as
needed. Monitor where the water is flowing at all times. Note the velocity
pressure on the remote gauge (hold gauge at the height of the 4 -1/2” outlet
when taking this reading). When the flow pressure has stabilized, notify the
S/R hydrant to take the residual pressure reading.
Section 403.003(b)
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Note: Residual pressure must not be dropped below 20 psi in order to avoid
damage to water pipes and creation of a potential backflow condition
from domestic water systems. Notify flow hydrant staff of a residual
pressure approaching 20 psi and cease opening the hydrant further to
maintain a residual pressure not less than 20 psi. This situation
typically will only occur where pipe sizes are less than 8 inch and
pumping capacity is insufficient.
10. Slowly close the flow fire hydrant to mitigate water surges; when fully closed,
the post flow S/R hydrant residual pressure also needs to be recorded. A
reading higher than the pre-flow reading will indicate that a well pump was
activated during the test.
11. Record all S/R and flow hydrant pressure readings and note the hydrant
number(s) where the readings were taken.
12. Disassemble all test equipment; restore hydrant caps, and double check the
test area for all tools.
Note: Always open the bleed valve on the S/R hydrant cap before closing the
hydrant valve to prevent a water hammer from damaging the gauge.
13. After the test, the fire prevention engineer will analyze the flow data, complete
Fire Prevention Division, Flow Test Result form, FPD-F-32, and scan the
document into the Fire Hydrant Flow Test folder on the K Drive. As a
courtesy, the test form should be sent to the applicable water purveyor for
their information.
PROCESS
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INFORMATION
The water supplies for the aforementioned water purveyors currently primarily come
from numerous water wells and pump stations throughout the metropolitan Fresno
area. Historically, pumping from these wells has resulted in a severe ground water
overdraft condition; wells must be drilled deeper and electrical costs for pumping
water significantly has increased. Both the State of California and local water
purveyors have restricted water use to certain days of the week and hours within the
day and imposed penalties for water wasting. Routine full flow testing of fire
hydrants will use +/- 2000 gallons per minute during the test and has a negative
Section 403.003(b)
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reaction from a public that is being continually reminded about the need to conserve
water.
Since the late 1980s, the Department has practiced water conservation by limiting
the flow of water during annual hydrant maintenance and providing fire protection
design engineers with prescriptive water flow curves based on the infrastructure of
the aforementioned water purveyors. Measured and documented full flow fire
hydrant testing has been limited to Insurance Services Office (ISO) mandated
surveys, specific high water demand projects, and to diagnose problems in the
existing water infrastructure. Both newly installed public and private fire hydrants
have to be flowed to remove debris from the pipe and insure the hydrant is operating
but these acceptance test flows are not typically measured.
Water flow testing is usually done during daylight hours both for staffing and
logistical reasons. In any 24 hour period, the highest domestic water consumption in
most of the city occurs between 0000 and 0600 hours daily with landscape irrigation.
Also, peak domestic water demand occurs in the summer months when lan dscape
watering is at its most demanding. The use of prescriptive water supply curves is a
methodology formulated to account for these water system operation parameters
and provides an inherent safety factor for fire protection design to account for peak
domestic demand periods and future growth patterns.
Prescriptive flow curves provided for fire protection design are as follows:
Curve A: 45 psi static/35 psi residual/flow of 1800 GPM (for 10 inch and
larger circulating transmission grid water mains---TGMs).
Curve B: 45 psi static/35 psi residual/flow of 1350 GPM (8 inch circulating
water mains connected to TGMs within ½ mile of the project site, 10 inch or
larger dead end water mains exceeding 1000 feet ).
Curve C: 40 psi static/25 psi residual/flow of 1350 GPM (other infrastructure
6 inch or larger not covered by A & B above).
These curves are based on City water system operating parameters and historical
production data. For the Pinedale, Bakman, and Malaga water purveyors , Curve C
must be used unless specifically determined otherwise by the fire prevention
engineer.
DEFINITIONS
1. Static Water Pressure: W ater system pressure present during periods of
domestic water consumption without any fire hydrant and/or fire protection
systems water demand.
Section 403.003(b)
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2. Residual Water Pressure: W ater system pressure present with a fire hydrant
and/or fire protection water demand plus domestic water use.
3. Velocity Pressure: A reading on a pitot gauge tool that is converted to gallons
per minute based on a mathematical formula using the factors of pitot gauge
pressure, diameter of the flow outlet, and coefficient of flow orifice discharge.
4. Fireflow: Available fire protection water supply in GPM at a residual pressure
of 20 psi.
5. Hose Monster Big Boy: A proprietary flow test diffuser with built in Factory
Mutual approved calibrated pitotless nozzle.
CROSS-REFERENCES
National Fire Protection Association (NFPA)
NFPA 291, Recommended Practice for Fire Flow Testing and Marking of
Hydrants
Fire Prevention Manual
Flow Test Result Form, FPD-F-32