Flow (gpm) and nozzle reaction (lbf) for smooth bore tips at their rated pressures — 50 psi for handlines, 80 psi for master streams.
Smooth bore (solid stream) tips deliver a predictable flow that depends only on the tip diameter and nozzle pressure. This chart lists the flow and the rearward nozzle reaction force for the standard handline and master stream tip sizes, so you can size lines and crew them safely.
GPM = 29.7 × d2 × √NP
NR = 1.57 × d2 × NP
| Tip Size | NP (psi) | Flow (gpm) | Reaction (lbf) | Typical Use |
|---|---|---|---|---|
| 7/8" | 50 | 161 | 60 | Handline |
| 15/16" | 50 | 185 | 69 | Handline |
| 1" | 50 | 210 | 79 | Handline |
| 1⅛" | 50 | 266 | 99 | Big handline (2½") |
| 1¼" | 50 | 328 | 123 | Big handline / blitz |
| 1⅜" | 80 | 502 | 237 | Master stream |
| 1½" | 80 | 598 | 283 | Master stream |
| 1¾" | 80 | 814 | 385 | Master stream |
| 2" | 80 | 1063 | 502 | Master stream |
Flows rounded to the nearest gpm. A widely used set of working limits (Paul Grimwood's) is about 60 lbf of nozzle reaction for one firefighter, 75 lbf for two and 95 lbf for three. Well-trained crews with good technique can hold more, but past those figures most crews struggle to control the line, which is why master stream tips are mounted to an appliance.
Flow grows with the square of the tip diameter, so small changes have a large effect. Stepping a handline from a 7/8" to a 1" tip at 50 psi raises flow from about 161 to 210 gpm — and raises reaction from 60 to 79 lbf. That is why tip selection is a deliberate tactical decision, not an afterthought.
For any tip size or pressure, use the free Smooth Bore Nozzle Flow Calculator and the Nozzle Reaction Calculator. To turn flow into a pump pressure, continue with the Pump Discharge Pressure Calculator and the friction loss chart. Choosing between nozzle types? See smooth bore vs. fog nozzles.
Both columns of the chart come from two standard fireground formulas, so you can compute any tip and pressure the chart doesn't list:
Worked example — 1⅛" tip at 50 PSI: flow is 29.7 × (1.125)² × √50 = 29.7 × 1.266 × 7.07 ≈ 266 GPM; reaction is 1.57 × 1.266 × 50 ≈ 99 lbf. That is just past the 95 lbf working limit for three firefighters, so a 1⅛" line needs a full, well-practised crew — which is exactly why the chart pairs every flow number with its reaction number.
Bigger tips buy flow at the cost of control. The working rule: pick the largest tip your staffing can hold for the duration of the attack, not the largest your pump can supply. A 15/16" tip at 185 GPM (69 lbf) is over the one-firefighter limit, so it wants a second firefighter backing up the nozzle; a 1¼" tip at 328 GPM (123 lbf) is well past the three-firefighter limit, so plan to flow it from a portable monitor or with a large crew braced on the line. For master streams the constraint flips — the device holds the reaction, so tip selection is about matching your water supply: there is no point flowing a 2" tip at 1,000+ GPM off a hydrant that delivers 800.
How many gpm does a 7/8-inch smooth bore tip flow? About 161 gpm at the rated 50 psi handline nozzle pressure, using GPM = 29.7 × d² × √NP.
What is the flow of a 1-inch smooth bore tip? About 210 gpm at 50 psi nozzle pressure. A 1¼-inch tip flows about 328 gpm at 50 psi.
What nozzle pressure do smooth bore tips use? Handline smooth bore tips are rated at 50 psi nozzle pressure; master stream smooth bore tips are rated at 80 psi.
How much nozzle reaction can a firefighter handle? A widely used set of working limits (Paul Grimwood's) is about 60 lbf for one firefighter, 75 lbf for two and 95 lbf for three. Well-trained crews with good technique can hold more, but past those figures most crews struggle to control the line, which is why master stream tips are mounted to an appliance.
What is the smooth bore nozzle reaction formula? NR = 1.57 × d² × NP, where d is the tip diameter in inches and NP is the nozzle pressure in psi. A 1-inch tip at 50 psi produces about 79 lbf of reaction.