Sprinkler Head Flow Rate Calculator
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Sprinkler Head Flow Rate Calculator
Calculate the flow rate through a sprinkler head using the K-factor formula. Enter the K-factor and pressure to determine the discharge flow rate.
K-Factor (gpm/psi½)
Common values: 2.8, 4.2, 5.6, 8.0, 11.2, 14.0, 16.8, 19.6, 22.4, 25.2
Pressure at Sprinkler Head
psi bar kPa
Minimum operating pressure is typically 7 psi (0.48 bar / 48.3 kPa)
Output Flow Unit
gpm (US gallons per minute) L/min (litres per minute) m³/h (cubic metres per hour)
Calculate Flow Rate
function sprCalc() { var resultDiv = document.getElementById('spr-result'); resultDiv.style.display = 'block';
var kFactor = parseFloat(document.getElementById('spr-kfactor').value); var pressure = parseFloat(document.getElementById('spr-pressure').value); var pressureUnit = document.getElementById('spr-pressure-unit').value; var flowUnit = document.getElementById('spr-flow-unit').value;
// --- Input Validation --- if (isNaN(kFactor) || kFactor ⚠ Please enter a valid K-factor greater than 0.'; return; } if (isNaN(pressure) || pressure ⚠ Please enter a valid pressure greater than 0.'; return; }
// --- Convert pressure to psi for formula --- var pressurePsi; if (pressureUnit === 'psi') { pressurePsi = pressure; } else if (pressureUnit === 'bar') { pressurePsi = pressure * 14.5038; } else if (pressureUnit === 'kpa') { pressurePsi = pressure * 0.145038; }
// Warn if below minimum recommended pressure var pressureWarning = ''; if (pressurePsi 175) { pressureWarning = '⚠ Warning: Pressure exceeds the typical maximum of 175 psi. Check system design.
'; }
// --- Core Formula: Q = K * sqrt(P) --- // Q in gpm, P in psi, K in gpm/psi^0.5 var flowGpm = kFactor * Math.sqrt(pressurePsi);
// --- Convert flow to selected output unit --- var flowDisplay, flowUnitLabel; if (flowUnit === 'gpm') { flowDisplay = flowGpm.toFixed(2); flowUnitLabel = 'gpm'; } else if (flowUnit === 'lpm') { flowDisplay = (flowGpm * 3.78541).toFixed(2); flowUnitLabel = 'L/min'; } else if (flowUnit === 'm3h') { flowDisplay = (flowGpm * 3.78541 * 60 / 1000).toFixed(3); flowUnitLabel = 'm³/h'; }
// --- Additional derived values --- var flowLpm = flowGpm * 3.78541; var flowM3h = flowGpm * 3.78541 * 60 / 1000; var pressureBar = pressurePsi / 14.5038; var pressureKpa = pressurePsi * 6.89476;
resultDiv.innerHTML = '### ✓ Flow Rate Result ' + '' + flowDisplay + ' ' + flowUnitLabel + '
' + pressureWarning + '' + 'ParameterValue' + 'K-Factor' + kFactor.toFixed(1) + ' gpm/psi½' + 'Pressure' + pressurePsi.toFixed(2) + ' psi | ' + pressureBar.toFixed(3) + ' bar | ' + pressureKpa.toFixed(1) + ' kPa' + 'Flow Rate (gpm)' + flowGpm.toFixed(2) + ' gpm' + 'Flow Rate (L/min)' + flowLpm.toFixed(2) + ' L/min' + 'Flow Rate (m³/h)' + flowM3h.toFixed(3) + ' m³/h' + ''; }
#### Formula
Q = K × √P
- Q = Flow rate (US gallons per minute, gpm)
- K = K-factor of the sprinkler head (gpm / psi½)
- P = Pressure at the sprinkler head (psi)
Unit Conversions used:
Example: A K-5.6 sprinkler at 7 psi: Q = 5.6 × √7 = 5.6 × 2.646 = 14.82 gpm
#### Assumptions & References
- The K-factor formula Q = K√P is defined in NFPA 13 (Standard for the Installation of Sprinkler Systems) and FM Global Property Loss Prevention Data Sheets.
- Pressure must be in psi and flow in gpm for the standard K-factor formula; metric K-factors use bar and L/min (Kmetric = Kimperial × 14.4).
- Minimum operating pressure for standard spray sprinklers is typically 7 psi (0.48 bar) per NFPA 13 §8.2.1.
- Maximum pressure at any sprinkler is typically 175 psi (12.1 bar) per NFPA 13 §8.2.2.
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