Standpipe System Design Calculator

Standpipe class and sizing from building height and use.

Standpipe class

Building height (ft)

Number of floors

Number of standpipes

Hazen-Williams C factor

Riser pipe diameter (in)

Tab to move between fields

Total system flow (GPM)

750

Total pressure needed (PSI)

146.6

Residual pressure (PSI)100

Static head loss (PSI)32.5

Friction loss (PSI)14.1

Pipe velocity (ft/s)19.1

Velocity acceptableNo

Min riser diameter (in)4

Total hose connections10

Friction loss (PSI/ft)0.16

How to Use This Calculator

Enter Standpipe class, Building height (ft), and Number of floors.
Set Number of standpipes, Hazen-Williams C factor, and Riser pipe diameter (in).
Review Total system flow (GPM) and Total pressure needed (PSI).
Use Residual pressure (PSI) and Static head loss (PSI) to inform your decision.

What each input means

Standpipe class: 1=Class I (2.5" FD use), 2=Class II (1.5" occupant use), 3=Class III (combined).
Building height (ft): Height from grade to highest standpipe outlet.
Number of floors: Total number of floors with standpipe connections.
Number of standpipes: Number of standpipe risers in the building.
Hazen-Williams C factor: Pipe roughness coefficient. 120=new steel, 100=aged steel, 150=CPVC/copper.
Riser pipe diameter (in): Internal diameter of the standpipe riser.

Total system flow (GPM): Total standpipe system flow demand per NFPA 14.
Total pressure needed (PSI): Required pump discharge pressure: residual + friction + static head.
Residual pressure (PSI): Minimum pressure at the most remote hose connection.
Static head loss (PSI): Pressure due to elevation (0.433 PSI per foot).
Friction loss (PSI): Pipe friction loss calculated by Hazen-Williams formula.
Pipe velocity (ft/s): Water velocity in the riser. Should not exceed 15 ft/s.
Velocity acceptable: Whether pipe velocity is within the recommended 15 ft/s limit.
Min riser diameter (in): Minimum pipe diameter per NFPA 14 for the selected class.
Total hose connections: Number of hose connections required across all floors and risers.
Friction loss (PSI/ft): Friction loss per linear foot of pipe.

Identify Input Parameters
4 parameters
Standpipe class = 1, Building height (ft) = 75, Number of floors = 5, Number of standpipes = 2 = 6 input(s) provided
Calculate Total system flow
Total system flow = flowPerStandpipeGPM + additionalFlow
750 = 750
Calculate Total pressure needed
Total pressure needed = residualPressurePSI + frictionLossPSI + staticHeadPSI
146.6 = 146.6
Calculate Residual pressure
Residual pressure
100 = 100
Calculate Static head loss
Static head loss = buildingHeightFt * 0.433
32.5 = 32.5