IFP Mag - Issue 35 digital edition

the fire sprinkler system demand. For instance,
given the original design curve and system
hydraulic demand point shown in Figure 1, the
water supply curve is reduced upon measurement
as graphically illustrated by the purple line (Curve
I) in Figure 3. In this case, the observed reduction
in the water supply strength is not expected to
affect the fire sprinkler system operation, since the
sprinkler system demand remains less than the
available supply curve as a result of a robust
pressure buffer. No additional remediation is
necessary for this case.
The grey line shown in Figure 3 represents a
second hypothetical flow test data set (Curve II)
obtained from hydrant flow testing. In this
instance, the water supply curve is exceeded by
the fire sprinkler system demand point. For this
scenario, the fire protection system will not
provide the water capacity and/or pressure to the
system as intended. To meet the sprinkler system
demand, a means to fortify the water supply is
necessary (e.g. installation of a fire pump, elevated
water tank, system piping, etc.). A fire protection
engineer or other qualified personnel (e.g. licensed
fire protection contractor) should be consulted to
evaluate the system design and implement an
appropriate solution based analysis of all relevant
details.
4 Test and calibrate pressure gauges
The data obtained from sprinkler system testing is
only as valid as the instruments used for measure-
ment. Relying on faulty pressure gauges can
produce inaccurate test results. Contractors
performing ITM services should be instructed to
inspect and test pressure gauges periodically
to verify proper operation. Based on NFPA 25,
Section 12.2.8, pressure gauges are to be
inspected on a monthly basis and replaced with a
calibrated gauge or tested every 5 years to be
within 3 percent of the full scale in comparison
with a calibrated gauge. A system for identifying
components and the date of replacement or
calibration (e.g. affixing unique identification
numbers and dates) should be incorporated as
shown in Figure 4.
Written records should identify the specific
gauges replaced or tested, and records should be
maintained for no less than 5 years after the next
inspection, test, or maintenance period. Requiring
a contractor to inspect and use properly calibrated
gauges can prevent the collection of misleading
test data.
5 Establish a management of change protocol
Performance of periodic ITM by qualified person-
nel is important in managing changes in water
supply conditions. As a start, records related to
these activities serve as a basis for monitoring
change and should be retained by the property
owner for reference. Most importantly, a protocol
should be developed in collaboration with the
parties responsible for ITM of the sprinkler system
to identify change, determine the impact, and
remedy the deficiency. In the event a sprinkler
system is impaired, administrative procedures for
notification and mitigation are presented in NFPA
25, Chapter 14, and should be included in the
protocol.
The protocol should include the investigation
procedures for use when a reduction in the water
supply is detected. A hydrant flow test upstream
of the sprinkler system may serve as a starting
point to determine the cause of the pressure
reduction. If the water distribution system is found
to be adequate, the cause of the reduction is likely
to be found between the point of connection
(POC) to the water utility and the sprinkler system
riser. System components from the POC, including
control valves, backflow preventers, and pressure-
reducing valves, should be inspected and tested
for proper operation. Additional direction is
provided by NFPA 25, Chapter 13, for investigating
fire protection system piping for possible sources
of materials that can cause blockage. After repairs
are made, the sprinkler system should be restored
and tested to verify hydraulic performance is
satisfactory.
Summary
Based upon international model fire codes, the
obligation for proper ITM of a building's fire
sprinkler system generally rests with the owner of
the property. Responsibility for these activities can
be delegated to a qualified contractor, but the
owner should stay involved to see that the
delegated tasks are being completed properly and
on a timely basis. Failure to conduct the required
ITM on the critical fire protection systems can
result in citations, fines, and possibly business
interruption. Improper ITM can also result in
undue risk for damages in the event of a fire and
improper sprinkler operation.
The successful operation of a fire sprinkler
system relies heavily on the characteristics of
the available water supply. An inadequate water
supply can cause improper operation during a
fire event leading to unnecessary fire damage.
Internationally recognized fire standards are
available and provide the requirements for ITM of
fire protection systems. The frequency of main
drain testing is often overlooked. Based on
industry standards, the testing can be on a
quarterly basis, depending on the water supply
configuration.
Original flow test data used for sprinkler system
design can be subject to significant change as a
result of diminished strength of the available water
supply. An initial water distribution flow test
should be performed for calibration and com-
parison to the sprinkler system design criteria
and hydraulic demand. Without such testing, the
main drain test may not detect a sprinkler system
that was constructed with an inadequate water
supply.
During the main drain test, any observed reduc-
tion in residual pressure should be investigated
immediately rather than waiting for a 10 percent
drop, as some sprinkler systems are sensitive to
small pressure changes. The impact on the sys-
tem's intended operation should be examined to
determine if the weakened supply is still adequate
to satisfy the system demand.
Properly calibrated gauges are necessary for
performing ITM, and a system to track the calibra-
tion date of equipment should be implemented. A
protocol to address changes in the sprinkler
system water supply should be developed in
collaboration with involved parties to outline
responsibilities, timing, and actions. Implementing
these steps will reduce the potential for an inade-
quate water supply to remain undiscovered. IFP
INTERNATIONAL FIRE PROTECTION 73
MANAGING CHANGE OF FIRE SPRINKLER SYSTEM WATER SUPPLIES
SPRINKLER TECHNOLOGY
Neil P. Wu, P.E., CBO is a
licensed Fire Protection
Engineer, a Certified Fire and
Explosion Investigator, a
Certified Building Official,
and a Managing Engineer at
Exponent, Inc., a scientific
and engineering consulting
firm.
17000 Science Dr., Ste 200,
Bowie, MD 20715
Email: nwu@exponent.com

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