Relay Pumping Max Distance
Maximum distance between pumpers in a relay.
Example
You enter
- Relay flow (gpm) 800
- Hose coefficient C (5 in LDH ~ 0.08) 0.08
- Pump max discharge (psi) 200
- Intake residual to hold (psi) 20
- Elevation gain (ft, negative = downhill) 10
You get
- Pressure budget 175.7 psi
- Friction loss per 100 ft 5.1 psi per 100 ft
- Maximum pumper spacing 3431
Checked against published worked examples from: IFSTA Pumping Apparatus Driver/Operator.
Details, formula, and sources
Scopebudget = max discharge - intake residual - 0.434 x elevation; FL_per_100 = C x (Q/100)^2; distance = budget / FL_per_100 x 100. The next intake needs 20 psi or it cavitates, and the distance falls with the square of flow. A planning aid, not incident command.
Formula or tablebudget = max_discharge - intake_residual - 0.434 x elevation; FL_per_100 = C x (target_flow / 100)^2; max_distance = budget / FL_per_100 x 100.
Source and editionIFSTA Pumping Apparatus Driver/Operator relay pumping maximum distance, by name.
Free accessThe relay-pumping relations are public fire-service training material; the SOP and the pump's real capability govern the actual relay.
What governsEstimate. AHJ and licensed professional govern.
API field namestarget_flow_gpm, hose_coefficient, max_discharge_psi, intake_residual_psi, elevation_ft, budget_psi, fl_per_100_psi, max_distance_ft
- Intake residual hold 20 psi at the next intake so the pump does not cavitateIFSTA Pumping Apparatus D/O
- Square-law spacing FL per 100 ft scales with (Q/100)^2, so doubling the flow quarters the distanceIFSTA / Hazen-Williams family