HomeMy WebLinkAbout410.004 - Fire Hydrant Flow Testing
Fresno City Fire Department
400 Fire Prevention Manual
SECTION 410.004 FIRE HYDRANT FLOW TESTING
PURPOSE
This policy has been established to provide direction to Fresno Fire Department (FFD
or Department) Fire Prevention Division staff members with the proper procedures for
completing and documenting a fire hydrant flow test.
APPLICATION
There are a number of water supply systems capable of providing service to fire
hydrants and fire sprinkler systems within the City of Fresno and contract service
areas. These systems include: The City of Fresno Water Division, Bakman Water
Company, Malaga County Water District, and Pinedale County Water District. There
are also a limited number of private water systems which are not connected to any of
the previously noted water purveyors (i.e. they are private water systems).
OPERATIONAL POLICY
Fire flow test is to only be completed under the field supervision of a Fire Prevention
Division Fire Prevention Engineer (FPE). For private fire hydrants, fire flow testing
may be completed by a C-16 licensed contractor, but the results of that testing will not
be used for fire protection system design unless approved by a Department FPE.
Water purveyors may also conduct fire flow testing on their own water system, but in
most cases, fire flow testing is deferred to the Department.
OPERATIONAL GUIDELINE
Prior to completed testing, the FPE in responsible charge shall first review the latest
edition of NFPA 291, Recommended Practice for Fire Flow Testing and Marking of
Hydrants.
Testing should target a reduction in static pressure to 10 psi below static pressure.
This pressure reduction guideline is what has been traditionally used in an attempt to
force adjacent water well pumps to start and requires a large amount of water to be
flowed for an extended period of time. Due to a number of factors (i.e., water
conservation efforts, the logistics of multiple simultaneous fire flow tests, etc.)
dropping residual pressures in the hydrant system to 10 psi below static pressure may
not be possible.
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 1 of 8
Equipment:
At a minimum, the following equipment is needed to conduct a fire hydrant flow test:
• Portable radios
• Printed copy of the flow test area image
• Suitable hydrant wrenches (incl. base pad & hydrant barrel located operating
valve wrenches)
• Four-and one-half inch (4-1/2”) Hose Monster brand, Big Boy water diffuser
with 0-60 psi liquid filled pressure gauge and remote reading kit
• Five-foot (5’) length of large diameter hose (LDH) (to be used to attach the
Hose Monster water diffuser to the hydrant)
• Hose Monster brand, Big Boy conversion chart for pitot gauge velocity pressure
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
• FPE Toolbox with adjustable wrenches, assorted pliers/screw drivers, and
small plumbing parts (including hose bib adaptor, various reducers to one
quarter (¼”) pipe thread, and a roll of Teflon tape)
Optional equipment:
• Extra set of hydrant wrenches
• Turnout boots
• Shovel
• Bolt cutters
• Twenty-five foot (25’) and Fifty foot (50’) lengths of LDH
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 2 of 8
• For multiple simultaneous hydrant flow testing, members should use additional,
conventional 4” flow tube and pitot tube with liquid filled gauge. Use velocity
pressure conversion table and orifice co-efficient factors from NFPA 291, for
determining flow gpm from conventional flow testing devices.
PROCESS
The responsible charge FPE (or their designee) must make a determination for the
best the flow test location using Department software (i.e., GIS I-View). Factors to be
considered when making this determination should include but are not limited to:
Water main and fire hydrant locations, avoiding high traffic areas, a location near the
project area or an area with similar water main infrastructure to the project location,
including relative distance to water well pump stations. It is recommended that the
FPE (or their designee) print the location (including the water main and hydrant layers)
for later use.
In the event a high-volume traffic area cannot be avoided, the FPE (or their designee)
must make arrangements to have proper traffic control in place prior to conducting the
test following Department protocol.
Traffic control efforts may also be aided by contacting the City of Fresno Streets
Maintenance Division of Public Works to temporarily reprogram adjacent traffic lights
to “all way” stop as needed.
The FPE (or designee) must ensure that the test is ready to be performed when traffic
control measures are in place in order to minimize impacts to the residents in the area,
other City departments and City staff. To help minimize any unforeseen delay, the
FPE (or designee) should complete a site survey prior to the test day verify the
affected hydrants are operational, and that there are no other conditions that may be
impacted by the testing, including effluent runoff, etc.
Hydrant Flow Test Procedure:
1. Notify Fire dispatch and Fire Prevention Division support staff of the flow test
location and estimated duration of the test. Opening and closing a flow hydrant
may result in water surges in the water system that may activate water flow
switches on nearby fire sprinkler systems. Additionally, flooding of streets or
the release of high volumes of water during drought conditions may result in
residents calling 911 or calls to Department Headquarters.
2. Verify the path that the flowing water will be drained to. Ensure that there are
no open construction trenches or other conditions which will be unduly
impacted by the water flowing from the hydrant. The flow diffuser will direct
water laterally parallel to the street, but large amounts of water may cause it to
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 3 of 8
“pond” in traffic lanes and create a traffic hazard. Care should be taken in areas
without curbs and gutters.
3. Begin traffic control operations as needed for a particular site. Verify each
member operating in (or adjacent to) a roadway is in proper traffic personal
protective equipment. Set up traffic cones to divert traffic away from the test
area. Provide sufficient space for vehicles to make traffic maneuvers into
adjacent lanes.
4. The recording member must note the hydrant number(s), and approximate
“addresses” where the readings will be taken.
5. Locate the pre-determined flow hydrant and verify it is operational. Remove
the four-and one-half inch (4-1/2”) cap and tighten the two, two-and one-half
inch (2-1/2”) caps.
6. Attach the five-foot (5’) length of LDH to the flow hydrant and connect the
diffuser. The diffuser should be placed in the curb and gutter when possible.
Connect the remote pressure reading tubing and velocity pressure gauge to
the diffuser quick connect coupling.
7. The static and residual pressure (S/R) gauge hydrant must be located
upstream from the flow fire hydrant on a dead end main, or for circulating mains,
located as close as possible to the project site for a higher degree of accuracy.
8. 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 small number of turns to obtain a static pressure
reading.
b. On the supply (purveyor) side of a reduced pressure (RP) backflow device
using one of the pipe adapters in the tool kit. RP devices have directional
arrows on the body indicating the 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 as landscape watering is not permitted during the day
(this information may be obtained by using the GIS I-View software and
verifying the irrigation service on the water plat information layer).
c. Prior to using this final method, obtain FPE approval, and approval from the
affected property owner. On a hose bib on an adjacent dwelling unit, using
the adaptor in the tool kit. There is no RP backflow device required for
dwelling units; the member must only verify that no water is being used
while the test is being conducted. Members should never place the S/R
gauge downstream of an RP backflow device.
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 4 of 8
9. Position one (1) member at each of the two-gauge locations described in #5
(flow hydrant) and #6 (S/R hydrant); establish communications via cellular
telephone, portable radios or hand signals. The member recording the
readings must have a suitable writing instrument and paper to record gauge
readings.
10.Upon notification from the flow hydrant member, the recording member should
record the static pressure at the S/R hydrant. The recording member should
be ready to record the residual pressure upon notification from the flow hydrant.
11.The member operating the flow hydrant should begin to open the flow hydrant
slowly and adjust the Hose Monster LDH as needed until the hydrant is fully
open. The member must monitor the discharging water at all times to maintain
a safe environment. The recording member must note the velocity pressure on
the remote gauge (hold gauge at the height of the four-and one-half inch (4-
1/2”) outlet when taking this measurement). Once water flow pressure has
stabilized, notify the S/R hydrant to take the residual pressure reading.
Note: Residual system pressure must not be allowed to fall below 20 psi in
order to avoid damage to the water system and/or to create a potential
backflow condition from domestic water systems. The S/R member
must notify the flow hydrant member once a residual pressure begins to
approach 22 psi and cease opening the hydrant further to maintain a
residual pressure not less than 20 psi. This condition is rare, and usually
only occurs where water main pipe sizes are less than eight inches (8”)
in diameter and water well pumping capacity is insufficient.
12.Once the measurements have been made, the member operating the flow
hydrant should begin to slowly close the flow hydrant to mitigate water surges.
Once the flow hydrant has been fully closed, the post flow S/R hydrant residual
pressure must also be recorded by the recording member. A measurement
which reads higher than the pre-flow measurement is an indication that a well
pump within the vicinity of the flow hydrant was activated during the test.
13.The member stationed at the S/R hydrant must open the bleed valve on the
S/R hydrant cap before closing the hydrant valve to prevent a water hammer
from damaging the gauge. Once bled down, members should disassemble all
test equipment and dry as needed. Once complete, reinstall the removed
hydrant caps on the affected hydrants.
14.Once completed, each member shall survey the test area for all tools, debris,
etc. Once the site survey has been completed, each member shall advise the
FPE (or designee) in responsible charge of the test that the sites are clear of
any tools, debris, etc.
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 5 of 8
Once the testing is completed, the responsible charge FPE will analyze the test data.
Once analysis is complete, the responsible charge FPE will complete the necessary
fire flow test results documentation.
As a courtesy to the affected water purveyor, all fire hydrant flow testing results should
be forwarded to the applicable water purveyor contact for their information.
INFORMATION
The water supplies for each of the water purveyors within the City and contract service
areas primarily come from numerous water wells and pump stations located
throughout the greater Fresno area. Historically, pumping from these wells has
resulted in a severe ground water overdraft condition; new wells must be drilled
deeper than previous wells, and electrical costs for pumping groundwater has
increased significantly. Both the State of California and local water purveyors have
restricted water use to certain days of the week, and hours within the day in an effort
to curb excessive consumption. The City has also imposed penalties for the excessive
use of water resources. Department estimates note that routine, full flow testing of
fire hydrants use at least 2000 gpm (+-) during testing, and usually generates a
negative public perception of the Department as a steward of one of our most valuable
natural resources. Additionally, unnecessary use of water for testing purposes is in
direct conflict with the residents that the Department serves, who are continuously
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. 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 must
be flowed to remove debris from the pipe and to ensure the hydrant is operating
correctly, but these underground water main and fire hydrant acceptance flow tests
are not typically measured.
Water flow testing is usually done during daylight hours for both staffing and logistical
purposes. Peak domestic water system demand usually occurs in the hotter, dryer,
summer months when landscape watering is at its most demanding. In any 24-hour
period during these hot dry months, the highest domestic water consumption in most
areas of the City occurs between 0000 hrs. and 0600 hrs. each day again, driven by
landscape irrigation activity. The Fire Prevention Division also limits water
consumption and unnecessary full flow hydrant testing by providing stakeholders with
prescriptive water flow curves for both building fire flow and fire sprinkler design.
These prescriptive curves are based on water main infrastructure in a project area,
historic data on available fire flow at peak demand periods, anticipated available fire
flow with future development, and the known operating parameters of the respective
water purveyors.
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 6 of 8
The use of prescriptive water supply curves for fire protection is a methodology
formulated to account for water system operation parameters and provides an
inherent (though unquantified) margin of safety for fire protection designers to account
for peak domestic demand periods, future growth patterns and other factors.
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 noted above are based on City of Fresno Water Division water system
operating parameters and historical production data. For projects serviced by the
Bakman Water Company, Malaga County Water District, and Pinedale County Water
District, Prescriptive Curve C must be used unless specifically determined otherwise
by the responsible charge FPE.
DEFINITIONS
1. Static Water Pressure: Water system pressure present during periods of
domestic water consumption without any fire hydrant and/or fire protection
systems water demand.
2. Residual Water Pressure: Water 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. Fire Flow: Available fire protection water supply in GPM at a minimum residual
pressure of 20 psi.
5. Hose Monster Big Boy: A proprietary flow test diffuser with built in Factory
Mutual approved calibrated pitotless nozzle.
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 7 of 8
CROSS-REFERENCES
National Fire Protection Association (NFPA)
NFPA 291, Recommended Practice for Fire Flow Testing and Marking of
Hydrants (Latest Edition)
Effective Date: May 2019 Justin H. Beal, Fire Prevention Engineer
Current Revision Date: 5/3/2024 Section 410.004
Next Revision (1) Date: 5/3/2027 Page 8 of 8