Features of Fire Flow Testing

Fire Flow Testing

Fire flow testing evaluates the water supply availability for firefighters in a given hydrant. The test also measures friction loss in piping systems due to hose and pipe characteristics.

Sprinkler contractors, engineers, and city planners need to understand the importance of fire flow analysis. The fire flow results browser allows you to check the zone and system pressure constraints and other results like pipe velocities and hydraulic grades.

Water is Safe to Consume

In a fire hydrant flow test, the system’s available fire flows are determined by measuring static and residual pressure at two hydrants. The “residual” hydrant measures the pressure at the hydrant without any hydrant flow, and the “flow” hydrant flows to measure how the water pressure drops during the hydrant flow test. The results are plugged into the formula to calculate available fire flow.

This type of test has limitations because it only evaluates one hydrant at a time and does not measure friction loss in the connection between the underground main and the hydrant. As a result, the hydrant capacity flow test does not accurately predict the flow rate firefighters will encounter at the hydrant.

Fire hydrant flow testing is critical for engineers, developers, contractors, and fire-suppression sprinkler companies. The data helps them ensure adequate water and pressure for domestic and fire water services, sizing fire-suppression sprinkler systems, and sizing booster pumps.

Water is Not Interrupted

Fire departments rely on the hydrants to provide water to extinguish fires. The hydrant capacity fire flow test verifies that the system works from the source to the hydrant nozzle.

The water data obtained from fire flow testing is used for many different purposes, including training firefighters, planning and marking hydrants, water system design and improvement, and calibration of hydraulic models. Engineers, developers, contractors, fire sprinkler companies, and insurance agencies often request this information.

During the fire flow analysis, there may be one or more nodes that are experiencing low pressures, but they will not cause a failure of the residual pressure constraint. To avoid these nodes from being checked, you can create a selection set to exclude them from the zones and system pressure checks. 

Water is Not Damaged

Flow tests are conducted by opening and closing fire hydrants to allow water to flow out of the valve. While this disturbs sediment naturally occurring in water mains, the disturbance cannot cause water damage. Water released during a fire hydrant flow test can temporarily appear rusty or discolored from this sediment stirring. The water is still safe to drink and clears within a few hours.

Fire hydrant flow testing allows engineers to uncover blockages or infrastructure problems that could result in an inadequate fire department water supply. It also helps sprinkler design companies accurately size their fire suppression systems for commercial and residential buildings.

During a fire hydrant flow test, a pressure gauge is placed on hydrant #1 to measure the static pressure (hydrant #2). The hydrant is then opened and closed to determine its available fire flow in gallons per minute. The available fire flow is based on the hydraulic model’s estimated average maximum day demand pressure and the head loss in the service/fire lines, hydrant, meters, and piping from the underground main to the hydrant.

Water is Safe for the Environment

Fire hydrant flow testing is an important and necessary process to verify that fire hydrants have enough water and pressure available for fire emergencies. All hydrants must pass this test to ensure firefighters have enough water to fight fires and identify hydrants needing repair.

Two fire hydrants are opened up to their maximum capacity during the hydrant flow test. One hydrant is closed, and a pressure gauge (the “residual hydrant”) is placed on it. The other fire hydrant is then opened up, and a hand-held pitot pressure gauge is used to measure the residual pressure during the test.

The pressures of the two hydrants are then combined with a formula to determine the flow rate achieved during the test. Using this information, engineers, sprinkler contractors, and commercial property developers can design systems to ensure adequate fire protection for the building.

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