Engine Operations › Hydraulics Calculator
Pump discharge pressure worked the way the standard works it — nozzle first, back to the pump. Every coefficient, nozzle pressure and appliance loss on this page is Orem’s.
Total lay from the pump to the nozzle.
5 psi per floor above the 1st · 0.5 psi per foot.
From the hydrant. Net pump pressure is PDP minus this.
Combined flow decides whether a small appliance counts 10 psi or 0.
Friction loss by coefficient.
The drill-ground shortcut.
| Hose | GPM | Field | C×Q²×L |
|---|---|---|---|
| 1-3/4" | 160 | 30 | 40 |
| 2-1/2" | 265 | 16 | 14 |
| 3" | 300 | 9 | 7.2 |
| 5" | 1,000 | 10 | 8 * |
One discrepancy in the source. The printed table shows .08 in the 5″ C×Q²×L column. That is the coefficient repeated, not a pressure — C·Q²·L at 1,000 gpm is 0.08 × 10² × 1 = 8 psi, which is what this page uses. Worth raising with the training committee.
| Nozzle | Type | GPM | NP psi |
|---|---|---|---|
| 7/8" tip | Smooth bore — hand line | 160 | 50 |
| 15/16" tip | Smooth bore — hand line | 185 | 50 |
| 1" tip | Smooth bore — hand line | 200 | 50 |
| 1-1/8" tip | Smooth bore — hand line | 265 | 50 |
| 1-3/16" tip | Smooth bore — hand line | 300 | 50 |
| 1-1/4" tip | Smooth bore — hand line | 325 | 50 |
| 1-3/8" tip | Smooth bore — master stream | 500 | 80 |
| 1-1/2" tip | Smooth bore — master stream | 600 | 80 |
| 1-3/4" tip | Smooth bore — master stream | 800 | 80 |
| 2" tip | Smooth bore — master stream | 1,000 | 80 |
| TFT Mid-Matic Blue | Fog | 150 | 100 |
| Elkhart Select-O-Matic | Fog | 200 | 100 |
| Elkhart Chief XD | Fog | 160 | 50 |
Orem rates the Chief XD at 50 psi, not 100. It is a fixed-gallonage nozzle and pumping it at fog pressure would badly over-pressurize it.
| Hose | Coefficient | Appliance | Loss |
|---|---|---|---|
| 1" | 150 | None | — |
| 1-3/4" | 15.5 | Wye · gated wye · siamese · reducer | 10 / 0 |
| 2-1/2" | 2 | Deck gun · ground monitor | 25 |
| 3" | 0.8 | Aerial master stream — pre-plumbed (T33) | 25 |
| 5" | 0.08 | Playpipe (Tiller 33) | 15 |
| Standpipe | 25 | ||
| Rapid Attack Monitor | 10 |
Training reference only. Every value is transcribed from the OFD Apparatus Driver/Operator Hydraulic Calculation Standards. Elevation follows that standard — geographical 0.5 psi per foot, structural 5 psi per floor above the first, sub-level a gain subtracted from the PDP. Verify against the current standard and your own rig before pumping.