Fixed Water Spray Systems — Engineering Calculators
Practical calculation tools for the engineering design of fixed water spray fire-protection systems. Based on well-established engineering equations.
Calculators
Water Demand
Design density & protected area to estimate required flow, hose-stream allowance and water-supply volume.
Nozzle Flow (K)
Solve Q = K·√P — compute flow, K-factor or pressure from any two inputs.
Pipe Velocity
Velocity in a pipe from flow and diameter, checked against the guidance limit.
Velocity / Normal Pressure
Velocity pressure (Pᵥ = k·Q²/D⁴) from flow and diameter, and the normal pressure available for discharge.
Fitting Equivalent Length
Convert fittings and valves to an equivalent straight-pipe length for the friction calculation.
Sequential Hydraulic Run
Accumulate flow and pressure from the most-remote nozzle toward the supply, with friction, elevation and nozzle demand per node.
Branch Node Balance
Balance branch flows at a junction to a common node pressure (hydraulic junction method), summing corrected branch flows.
Nozzle Spacing & Coverage
From design density and per-nozzle flow, derive protection area per nozzle, spacing and nozzle count.
Pipe Friction Loss
Friction pressure loss along a pipe using the Hazen–Williams equation.
Elevation Pressure
Static pressure resulting from vertical elevation difference and back-calc of required head.
Water Supply Curve (Graph Sheet)
From a hydrant flow test (static, residual, flow) plot the water-supply curve against the system demand curve and read the adequacy margin.
Fire Pump Curve
Plot the fire-pump characteristic (churn, rated and 150% flow points) against the system demand curve and read the pressure margin.
Pump + Supply Combined Curve
Combine the fire-pump characteristic with the water-supply curve into a single available-pressure curve and compare it with the system demand.