Sprinkler Hydraulic Calculator
Pick the standard and hazard, set the head layout and pipe sizes, and the lab works out the most remote design area node by node with Hazen-Williams. You get the flow and pressure the system needs, checks it against your fire pump or water supply, and sizes the tank.
How to use: every input already has a sensible default. Change what you know, tap i next to any field for a plain explanation, and watch the results update.
1. Design basis
Standard, hazard and layout. Defaults follow the selected standard.
2. Most remote design area
Operating heads, flow in each pipe and pressure at each head. Tap a head to read its values.
3. Checks
4. Supply against demand
Hydraulic graph on a Q1.85 scale, so the supply curve and pipe losses plot as straight lines.
5. Node by node calculation
Hazen-Williams: p = 6.05 × 105 × Q1.85 / (C1.85 × d4.87) bar/m, with Q in L/min and d in mm. Head flow q = K√P.
6. How the calculation works
Density and area
Each hazard class has a design density (water per square metre per minute) that must be delivered over a design area at the most hydraulically remote part of the system. Every head in that area must give at least density × coverage, and at least the minimum pressure.
Shape of the area
The area is a rectangle with its long side along the branch lines, at least 1.2 × √A long. That sets how many heads flow on each branch. The remaining heads fill the next branches towards the cross main.
Balancing the branches
The remote branch is worked head by head. Each further branch is treated as one large sprinkler with its own K-factor (Q / √P) and flows at whatever pressure the cross main gives it, which is how hand calculations and software balance a tree system.
Back to the source
Friction in the feed main and riser, the valves and fittings, and the static height (0.0981 bar per metre) are added to give the pressure needed at the pump or valve set. Hose allowance is added to the flow, then the point is checked against the supply curve.
This is a learning and checking tool for tree systems with an end-fed cross main. Final designs need calculation in listed software, the sprinkler and valve data sheets, and the authority's approval.