What is the term for the pressure exerted by a stationary column of water, directly proportional to the height of the column?

What is the term for the pressure exerted by a stationary column of water, directly proportional to the height of the column?

• A. Proportioning
• B. Expellant Gas
• C. Total Flooding Systems
• D. Head Pressure

Answer: (D)

Pressure from a stationary column of water is called head pressure. It arises from the hydrostatic principle: the pressure at the bottom of the column is proportional to the height of the water above it, since P = ρ g h. In fire protection terms, head pressure is the pressure created solely by the height of the water column when no water is flowing. For example, a 100‑foot column produces about 43 psi of head pressure at the base (roughly 0.433 psi per foot). This is static pressure, not the pressure you get from pumping or during flow, which would include friction losses and dynamic effects. The other terms shown don’t describe this height-related static pressure: proportioning is about mixing for foam or other agents, expellant gas refers to a different extinguishing method, and total flooding systems describe system types rather than the pressure generated by water height.

Pressure from a stationary column of water is called head pressure. It arises from the hydrostatic principle: the pressure at the bottom of the column is proportional to the height of the water above it, since P = ρ g h. In fire protection terms, head pressure is the pressure created solely by the height of the water column when no water is flowing. For example, a 100‑foot column produces about 43 psi of head pressure at the base (roughly 0.433 psi per foot). This is static pressure, not the pressure you get from pumping or during flow, which would include friction losses and dynamic effects. The other terms shown don’t describe this height-related static pressure: proportioning is about mixing for foam or other agents, expellant gas refers to a different extinguishing method, and total flooding systems describe system types rather than the pressure generated by water height.