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Background of Hydraulic Calculations

Last updated 4 years ago

At first glance, sprinklers seem like simple devices. Performing hydraulic calculations is as much an art form as a science. The term hydraulic calculations refers to the calculations required to determine whether the water available from the street (public water main), roof tank, or fire pump, has enough pressure (measured in pounds per square inch) and flow (measured in gallons per minute) for sprinkler heads to operate properly.

To understand hydraulic calculations, it is first important to grasp the advantages of water in a fire suppression system:

     1. Water is a remarkably effective extinguishing agent. In order to extinguish, suppress or control a fire, one of three parts to the fire triangle must be removed. The fire triangle describes the parts required for sustainable combustion. They include an oxidizer (air), heat, and fuel. When used to extinguish a fire, water attacks all three parts. First, due to the temperature, water will evaporate into vapor, displacing the oxidizer in the room. Second, due to the heat capacity of water, it will absorb heat, reducing the temperature below that which is required for combustion. Third, water will mechanically push the fuel around, physically reducing the mass of the origin fire.

     2. Water is economical (especially relative to non-water based suppression agents).

     3. Water is readily available.

     4. Water has predictable physical qualities. 

Hydraulic calculations are based on the science of hydrostatics (water at rest) and hydrokinetics (water in motion). When determining the adequacy of the flow and pressure of the sprinkler system, it’s critical to account for the pressure loss due to gravity, as well the friction caused by the water flowing through piping. The most widely recognized formula for determining this pressure loss is called the Hazen-Williams formula.

Finally, the building hazard determines how much pressure and flow will be required. For example, a light hazard occupancy, like an office building, will have significantly less pressure and flow requirements than a warehouse storing ketchup in plastic containers (Group A plastic). 

Capitol Fire Sprinkler has been serving NYC for over 60 years. If you want to learn more about the importance of hydraulic calculations, call us at (718) 533-6800 and talk to one our fire sprinkler experts. Whether you simply need information or require repairs to be up to code, Capitol Fire Sprinkler has a long history and a track record of success. 


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