What Is the K-Factor in a Sprinkler?

Representation

• The K-factor is the number of liters of water that flows through the sprinkler for each bar of water pressure. A bar is the standard air pressure at sea level. It is measured with specialized equipment. This is a vital statistic when calculating the capacity of a sprinkler system. The K-factor is often stated in a manufacturer’s information furnished with sprinkler heads.

Variables

• Architects and engineers need to know the amount of water that moves through the sprinkler head at a given water pressure. That's because if water flow in a building's water line is insufficient to combat a fire, the building is at risk. Building design experts commonly calculate water flow based on the K-factor and water pressure during the building design stage.

Significance

• While water pressure varies during the day, the K-factor, defined as an amount of flow at a given pressure, remains consistent. For example, if the pressure varies from 0.5 to 1.0 bars during a day, the engineer can plot how much water will flow through the sprinkler at each water pressure. If the flow of water at the minimum pressure is not sufficient to fight a fire, a higher K-factor sprinkler may be needed.

Suggested K-Factors

• A sprinkler with a K-factor of about 57 is sufficient for areas with minimal hazards, such as concrete buildings. This increases to about 115 for areas with more serious fire hazards, such as buildings that house flammable or explosive contents. Most systems require at least 0.5 bars for operation.