Pressure · elevation · unit conversion · hydraulic reference
Pressure / Head Converter
Elevation Pressure Change
Common Floor Heights
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Elevation Diagram
Common pressure-to-head conversions for fire protection design. Values based on water at standard conditions (62.4 lb/ft³).
| PSI | Feet of Head | Bar | kPa | Meters of Head | Context |
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This tool converts between pressure units (PSI, bar, kPa) and head units (feet of water, meters of water) used in fire protection and hydraulic engineering. It also calculates the pressure change caused by elevation differences — essential for standpipe, high-rise sprinkler, and water supply calculations.
Water weighs 62.4 pounds per cubic foot at standard conditions. A 1-foot column of water exerts 0.433 PSI at its base. Conversely, 1 PSI supports a column of water 2.31 feet tall. This relationship is the foundation of all elevation pressure calculations in hydraulic design.
In fire protection hydraulic calculations, elevation changes must be accounted for in every pipe segment. Water flowing uphill loses pressure at 0.433 PSI per foot; water flowing downhill gains pressure at the same rate. This applies to both sprinkler and standpipe systems.
For standpipe systems, the elevation component can be the largest single pressure demand — a 10-story building has roughly 100 feet of elevation, which translates to about 43 PSI of pressure just to push water to the top floor before any friction loss or residual pressure requirements.
When static pressure at hose valves exceeds code limits (typically 175 PSI per NFPA 14), pressure reducing valves or pressure restricting devices are required. Use this calculator to estimate static pressure at each floor based on pump discharge pressure and elevation.
Water weighs 62.4 lb/ft³ at standard conditions. A 1-foot tall column of water with a 1 square inch base weighs 62.4/144 = 0.433 pounds, which exerts 0.433 PSI. The inverse is 1/0.433 = 2.31 feet per PSI.
Yes. When water moves upward against gravity, it loses 0.433 PSI for every foot of elevation gain. When water moves downward with gravity, it gains 0.433 PSI per foot. This is independent of friction loss, which is always a loss regardless of direction.
No. Elevation pressure depends only on the vertical height difference, not on pipe diameter, flow rate, or pipe length. A 2″ pipe and an 8″ pipe lose the same 0.433 PSI per foot of elevation. Friction loss (which does depend on pipe size and flow) is calculated separately.
Start with your pump discharge pressure or city supply pressure. Subtract the elevation change to the highest hose valve (feet × 0.433). Then subtract friction loss through the piping. The remainder is the pressure available at the hose valve. If static pressure at lower floors exceeds 175 PSI, PRVs are needed.
Slightly. The 0.433 factor is based on water at about 60°F (62.4 lb/ft³). Hot water is less dense, so the factor decreases slightly. For fire protection design at normal water temperatures, the difference is negligible and 0.433 is standard.
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