Velocity Calculations
Nominal Diameter mm
Formula: V = 21.22 Γ Q Γ· DΒ²
Q in L/min Β· D internal in mm Β· V in m/s
Friction Loss
Calculate friction through one or more pipe sections. Flow and starting pressure remain constant.
Nominal Diameter mm
Hazen-Williams:
Pf = 6.05Γ10β· Γ QΒΉΒ·βΈβ΅ Γ· (CΒΉΒ·βΈβ΅ Γ Dβ΄Β·βΈβ·)
Pf in kPa/m Β· Q in L/min Β· D internal in mm
Q / P / K Factor
Enter any two values. Set the unknown to 0 to solve.
Q = K Γ βP
Q in L/min Β· P in kPa
Q / P / K Curves
Flow vs pressure curves for standard sprinkler K-factors.
Select K-Factors to display
Q = K Γ βP
Standard K-factors: 5.7 Β· 8.0 Β· 11.5 Β· 16.1 Β· 20.0 Β· 24.2 Β· 32.0 Β· 36.0
Starting Point
Calculate first sprinkler flow and pressure from design parameters. Control mode per ASIB 12th Edition.
Starting Point β Control Mode
Q = density Γ range spacing Γ sprinkler spacing
P = (Q Γ· K)Β²
Feed Mains
Calculate how flow splits through a ring main and the resulting friction loss.
Convert a ring main to an equivalent single pipe length for use in continuous friction calculations.
Nominal Diameter mm
Ring Main Flow Split:
A = long leg + fittings Β· B = short leg + fittings
Q_long = Q Γ· ((AΓ·B)β°Β·β΅β΄ + 1)
Q_short = Q β Q_long
Equivalent Length:
A = long leg + fittings Β· B = short leg + fittings
E = (1 Γ· ((AΓ·B)β°Β·β΅β΄ + 1))ΒΉΒ·βΈβ΅ Γ A
Friction = Pf(Q) Γ E
Cut Length
Calculate actual pipe cut length and elevation from floor coverage and roof pitch angle.
Cut Length: L = F Γ· cos(ΞΈ)
Elevation: E = L Γ sin(ΞΈ)
Two Diameters in One Pipe
Given a total pipe length and allowable friction loss, calculate how much of each diameter to use.
Preferred Diameter mm
Alternate Diameter mm
Method: Split pipe run so total friction = allowable
L_alt = (Pfβ Γ L β Allowable) Γ· (Pfβ β Pfβ)
L_pref = L β L_alt
Convert Diameter
Convert a pipe section to equivalent length in a different diameter.
Installed Diameter mm
Convert To Diameter mm
Factor: (D_installed Γ· D_target)β΄Β·βΈβ·
Equivalent: Factor Γ (Length + Fittings)
Convert Cumulative
Convert multiple pipe sections to equivalent length in one common diameter. Add sections one at a time.
Common Diameter mm
Existing Diameter mm
Factor: (D_common Γ· D_existing)β΄Β·βΈβ·
Equiv: Factor Γ (Length + Fittings)
Cumulative total of all sections
Flow Correction
Correct and combine flows from two different pressure zones.
Corrected: Q_corr = β(P_high Γ· P_low) Γ Q_low
Total: Q_high + Q_corrected
Circular Suction Tank
Calculate tank volume, dimensions and usable capacity. Set any one value to 0 to solve.
Sump Installed
Volume: V = Ο Γ RΒ² Γ H
Usable = Gross β Dead Water β Freeboard
Rectangular Tank
1.22m panel tank. Enter number of panels for each dimension. Set any one dimension to 0 to solve.
Sump Installed
Panel: 1.22m Γ 1.22m Β· Max height 6.1m (5 panels)
V = L Γ W Γ H Β· Usable = Gross β Dead β Freeboard
Atmospheric Pressure
Calculate available atmospheric pressure at a given altitude above sea level.
Barometric Formula:
P = 101.325 Γ (1 β 2.25577Γ10β»β΅ Γ E)β΅Β·Β²β΅β΅βΈβΈ
Below 150m: P = 101.325 kPa (sea level)
NPSHa β Suction Line
Net Positive Suction Head Available. Uses C=120 for suction pipe friction.
Suction Diameter mm
NPSHa = (P_atm β Safety β Vapour) β Friction Β± Static
Safety: 15 kPa Β· Vapour: 3.2 kPa Β· Friction uses C=120
Orifice Plate
Calculate orifice plate diameter from pipe, flow and required pressure drop.
Calculate pressure drop across a known orifice diameter at a given flow.
Calculate flow through a known orifice diameter at a given pressure drop.
Calculate orifice diameter from Bernoulli's equation with discharge coefficient Cd = 0.82.
Pipe Diameter mm
Size: d = D Γ· β΄β((βP Γ DΒ² Γ 0.04024 Γ· Q)Β² + 1)
K = Q Γ· βP
P Drop: P = (1.5625Γ10βΈ Γ QΒ²) Γ (Dβ΄ β dβ΄) Γ· (253009 Γ dβ΄ Γ Dβ΄)
Flow: Q = β(P Γ 253009 Γ dβ΄ Γ Dβ΄ Γ· (1.5625Γ10βΈ Γ (Dβ΄ β dβ΄)))
Bernoulli: A = Q Γ· (Cd Γ β(2gH))
d = 2 Γ β(A Γ· Ο) Β· Cd = 0.82
Orifice Table Lookup
Size orifice plate from standard test pipe tables (200, 150, 100, 80mm).
Test Pipe Diameter
Method: Pressure ratio A = P Γ (5000Γ·Q)Β²
Interpolate orifice Γ from standard table
K = Q Γ· βP
Water Supply Curve
Plot supply curve from static pressure test data. Also generates Q/P coordinate pairs.
Curve Lookup
Enter a flow or pressure to find the corresponding value on the supply curve.
Supply Curve: P = S β (QΓ·Q_test)ΒΉΒ·βΈβ΅ Γ (S β P_test)
Safety: β50 kPa applied to standing and residual
Pressure Switch Settings
Calculate pressure switch settings for jockey, primary and secondary pumps per rule 2038.
Pump Configuration
Jockey IN: β₯ 90% of churn
Primary PS1: 80% of churn Β· Gap β₯ 100 kPa (churn > 1000) or β₯ 50 kPa (churn β€ 1000)
Diesel PS2: 20β50 kPa below PS1
Secondary: β₯ 60% of churn, β₯ 100 kPa below primary PS1
Pump kW Absorbed
L/min & kPa: kW = QΓP Γ· (611.668 Γ eff%)
mΒ³/h & metres: kW = QΓP Γ· (3.67 Γ eff%)
Affinity Laws
Qβ = Qβ Γ (NβΓ·Nβ)
Pβ = Pβ Γ (NβΓ·Nβ)Β²
kWβ = kWβ Γ (NβΓ·Nβ)Β³
Pump Duty Curve
Plot pump curves from test data β with suction tank, without, and at reduced churn (β50 kPa).
Without tank: P = C β (QΓ·Q_t)ΒΉΒ·βΈβ΅ Γ (C β P_t)
With tank: P = (C+S) β (QΓ·Q_t)ΒΉΒ·βΈβ΅ Γ (C+S β P_tβS)
Reduced: Cβ50 kPa applied
Pump vs System Curves
Plot pump and system demand curves. Calculates intercept points for remote and favourable areas.
Pump Test Data
Remote Area
Favourable Area
Intercept: I = ((CβA) Γ· ((CβP)Γ·QΒΉΒ·βΈβ΅ + (EβA)Γ·BΒΉΒ·βΈβ΅))β°Β·β΅β΄
A=elevation, E=design P, B=design Q
Supply with Orifice
Plot supply curve reduced by orifice plate pressure drop, with optional demand curve overlay.
Pipe Diameter mm
Demand Overlay
Remote Area
Favourable Area
Supply: P = S β (QΓ·Q_test)ΒΉΒ·βΈβ΅ Γ (S β P_test)
Orifice ΞP: (1.5625Γ10βΈ Γ QΒ²)(Dβ΄βdβ΄) Γ· (253009 Γ dβ΄ Γ Dβ΄)
Reduced: Supply β Orifice ΞP at each flow
Diesel Engine kW
Calculate diesel engine power requirement with altitude and temperature deration factors.
Engine Type
kW: (Q Γ 60 Γ· 1000) Γ (P Γ· 10) Γ· (3.67 Γ eff)
Altitude: ((Hβ150)Γ·300 Γ F) Γ kW
Temperature: ((Tβ30)Γ·5.5 Γ G) Γ kW
