Tool

Standpipe Pressure Calculator

Walk through starting pressure, elevation loss, backflow, and friction loss for crossmains and risers to verify pressure at the top outlet.

Fire Protection Pressure Calculator

Walk through starting pressure, elevation loss, backflow, and Hazen-Williams friction loss for crossmains and risers.

Project name

Starting PSI

City residual pressure (psi)

City flow (GPM)

As noted on the hydrant flow test letter.

Pump pressure (psi)

As noted on the plan in the pump legend.

Pump flow (GPM)

Used for Hazen-Williams friction loss.

Total residual pressure

180.0 psi

Combined city and pump pressure.

Elevation Loss

Building height (ft)

From grade level to top floor.

Pressure loss per foot

0.433 psi

Standard elevation loss constant.

Total elevation loss

65.0 psi

At the top of the building.

Backflow Preventer

Backflow preventer loss (psi)

Backflow will usually deduct 7 psi unless otherwise noted.

Friction Loss

Hazen-Williams calculation using pump flow, pipe schedule, and fitting counts.

Pipe material / C-factor

Crossmain

Crossmain size

Schedule

Size

Select inside pipe diameter of crossmain.

Crossmain length (ft)

Length of crossmain excluding vertical riser.

Branch tees

Straight tees & elbows

Fittings loss

14.84 psi

Crossmain loss

16.86 psi

Risers

Riser size

Schedule

Size

Branch tees

Straight tees & elbows

Fittings loss

2.02 psi

Riser loss

4.21 psi

Riser pipe length equals building height (150 ft).

Total friction loss

37.93 psi

Summary

Total required at top (psi)

Total at top of riser

70.1 psi

Safety margin

5.1 psi

Extra pressure over the required 65 psi.

Engineering disclaimer

Results are for preliminary engineering only. Final designs must be reviewed by a licensed fire protection engineer and verified against NFPA 13/14 and the local AHJ.

Export report

Download a formatted PDF with inputs, loss breakdown, and pass/fail summary for your records or submittal package.

Pressure at top of riser

Pass

Total at top of riser: 70.1 psi
Total required: 65.0 psi
Safety margin: 5.1 psi

Loss breakdown

Total residual pressure: 180.0 psi
Elevation loss: 65.0 psi
Backflow preventer: 7.0 psi
Crossmain friction: 31.69 psi
Riser friction: 6.24 psi
Total friction loss: 37.93 psi

Hydraulic inputs

City residual: 60.0 psi @ 500 GPM
Pump: 120.0 psi @ 1000 GPM
Crossmain: Sch 10 - 6"
Riser: Sch 10 - 6"
C-factor: 120