Your building design is complete, and the time has come to start the construction process. Like with most projects, the due diligence phase is necessary to understand the project’s schedule, associated costs, and possible hurdles. One aspect of the due diligence phase involves fire protection, including requirements for fire sprinkler installation or meeting the locally codified fire flow requirements, which is the quantity and duration of water required to be available by fire hydrants or similar appurtenance for firefighting purposes. How can a building owner determine if a facility has enough water at the required pressure?
This is where a water supply analysis presents the greatest benefit. A fire protection professional, such as Telgian Engineering & Consulting (TEC), can perform a water supply analysis of the area immediately around the proposed location. Early water analysis can prevent costly construction delays and inform the builder/owner of the possible infrastructure requirements or alternate means of providing the necessary water supply.
What is a Water Supply Analysis?
NFPA 291: Recommended Practice for Fire Flow Testing and Marking of Hydrant, 2022 edition, Section 4.1.1, describes the purpose of water flow testing; “Water flow tests are conducted to determine the available water supply for fire protection purposes, the flow that would be available from a fire hydrant for firefighting purposes, or the status of the water supply distribution system for fire protection systems or for firefighting purposes.” Essentially, these tests help determine if there is sufficient water, at the necessary pressure, to effectively fight fires and support fire protection systems in a building or area.
Water flow testing utilizes two or more fire hydrants or other ports for measuring pressures to understand what is available at or near a building. This is a mode of gathering data to analyze three attributes of the water supply:
- Available pressure while static (not flowing)
- Residual pressure on the system while flowing another hydrant, preferably downstream
- The actual, observed flow rate, which is measured in the US as gallons per minute (gpm)
Considerations Before Testing
Before a fire protection expert performs a test, it is essential to understand why they are testing and what details are required to provide an accurate analysis. The three key factors are water volume, water pressure, and water source limitations.
Water Volume
Before a fire protection expert performs any testing, they must determine the available water source. Water can be supplied to any building via myriad modalities:
- Jurisdictional-provided water mains
- Above-ground and elevated storage tanks
- In-ground cisterns
- Onsite, private wells
- Ponds, reservoirs, streams, oceans, or lakes
- Other means
The water source can supply the building with what it needs if it can hold enough water. Once the water source has been identified, the requirements of the connection to said source shall be in accordance NFPA 13 – Standard for the Installation of Sprinkler Systems, NFPA 22 – Standard for Water Tanks for Private Fire Protection, NFPA 24 – Standard for the Installation of Private Fire Service Mains and Their Appurtenances, and/or any other locally requirements.
Water Pressure
Having water on hand is only half the battle; sufficient water pressure must also be available. This is often achieved by utilizing gravity with elevated storage tanks on stilts or a nearby hillside, installing a pump(s), or combining both.
Water Source Limitations
Most of the time, jurisdictions supply water through an underground main near a facility. When this is the case, a strong understanding of the water system is necessary to determine the selection of hydrants for testing, the point of connection for the system(s), and the system’s limitations. Some critical factors that help fire protection consultants determine the limitations and how they might affect the building are:
- What is the elevation of the test hydrant?
- What is the proposed elevation of the building’s finished floor?
- Where are the water treatment plant and the nearest pump and/or tank (for distance) located?
- If it is an elevated tank, what are the full and low levels of the tank?
- If the system employs direct pumping to maintain pressure, at what pressure does the pump turn on, and is it a variable speed pump or not?
- Are there pressure-regulating valves in the system (typical of ground storage tanks in nearby hills that provide water to the jurisdiction below)?
- Is the building in a gridded, looped, or dead-end portion of the system?
- What is the size and type of main (i.e., ductile iron, PVC, etc.)?
- Is the system currently being treated for microbial-inducing corrosion (MIC)?
- Any other factors that might affect the quality and quantity of water?
Water Supply Testing Procedures
Water supply tests should be performed with specialized equipment and only by trained professionals, such as fire protection engineers or the local fire or water departments (if offered).
The testing procedures are as follows:
- Rules for testing
- Testing should be conducted during periods of peak demand, during times when the most significant use of the system is occurring, i.e., if the project is near a residential area, the peak time might be in the morning around 8:00 am, when people are getting ready for work and yard sprinklers are running.
- Results with residual pressure below 20 psi are generally not accepted.
- The water supply tester should visually inspect the area around the flowing hydrant(s) for safety concerns.
- The tester should give consideration to potential interference with traffic flow patterns, damage to surroundings, and potential flooding problems (both local and remote from the site)
- The procedure consists of discharging water at a measured rate of flow from the system at a given location and observing the corresponding pressure drop (residual pressure).
- The hydrant selected as the test hydrant, which is gauged for static and residual pressures, should be as close to the point of the proposed or existing connection.
- Before the flow hydrant is opened, static pressure at the test hydrant is recorded.
- The flow hydrant should then be opened carefully and completely, and the full-flow rate should be recorded.
- Simultaneously, the residual is recorded at the test hydrant.
- After residual pressure and flow rate have been recorded, the flow hydrant is closed.
There are two items the water supply tester should keep in mind when analyzing the water supply:
- Is there enough pressure as required for the sprinkler system or 20 psi for fire flow? If not, then a booster pump will have to be installed; a booster pump only increases pressure, not volume.
- Is there enough volume of water available for firefighting purposes1? If not, then an additional mode of storage will be required (i.e., water storage tank, in-ground cistern etc.).
Note 1: Water supply requirements are to be determined by an industry professional
Project Example
A builder presented TEC with a site drawing for a gas station and mini-mart prepared by a civil engineer. The civil engineer’s assessment called for two (2) 100,000-gallon storage tanks and a 2,000-gpm booster pump to be installed. That engineer referenced only Appendix B of the California Fire Code but did not consider any reduction for a fully sprinklered building.
TEC immediately contacted the authority having jurisdiction (AHJ) and learned that they accepted the utilization of NFPA 1142. TEC then made calculations in accordance with that standard and found that the required quantity of water was only (1) 65,000-gallon water storage tank and a 500-gpm pump, as the water only needed enough pressure to support the sprinkler system inside of the mini-mart. Our findings significantly reduced the cost of the fire protection systems and helped the project stay under budget.
TEC’s Water Supply Services
TEC’s water supply services include:
- Water Supply Site Summary (WSSS): A full analysis of existing conditions
- Water Supply Investigations: Analysis of degraded water supplies with recommendations
- Water Flow Testing: Onsite water flow tests to determine available water availability
- Code & Jurisdictional Requirements Analysis: Review and application of local requirements
Conclusion
Conducting an early water supply analysis is crucial for meeting fire protection requirements and preventing costly delays during construction. Telgian Engineering & Consulting (TEC) is equipped to perform comprehensive water flow analysis and deliver detailed Water Supply Site Summaries (WSSS) tailored to your location’s specific needs. By engaging with local authorities and leveraging our nationwide expertise, TEC can provide the necessary analyses and recommendations to streamline your project from concept to completion.
Contact TEC today to schedule your water supply analysis to keep your project on track.
About the Author
Michael Willis, CFPS has 17 years of experience in fire protection and consulting. He has served as a leader in multiple fire protection roles including technician, inspector, consultant, installer and designer. His expertise includes code consulting, analysis and recommendations for both passive and active fire safety systems that feature special emphasis on life safety, suppression, special hazards and signaling.
Michael a member of Society of Fire Protection Engineers (SFPE) International and the Southern California Chapter of SFPE.
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