System specs
The numbers behind the water
A wildfire system is only as good as the water it can actually deliver. Here is how a FireShield system is sized — flow per zone, pipe, pressure, rotor throw, pump, foam — with a worked example for a real-size property and a calculator for your own pool or tank.
How it is built
The standard building blocks
16–20 GPM per line
Each zone line is designed for about 16 to 20 gallons per minute — enough to wet a roof edge or a side of the house, small enough that a household supply or a pool pump can keep up.
1-inch pipe, copper preferred
One-inch lines, copper where we can. Copper holds up to radiant heat and UV far better than plastic on an exterior wall.
Backflow preventer
Keeps system water, and any foam, out of your drinking water. Required on every connection to the street supply.
Pressure regulator
Holds the system at its design pressure so heads throw where they were aimed and fittings are not over-stressed.
Water-hammer arrestor
Absorbs the pressure spike when a valve closes, protecting joints and the controller’s valves.
Booster pump (optional)
Where street pressure is low, a booster brings it up to the design pressure before it reaches the zones.
Pool or tank pump
Default: 3 HP, three-phase, driven by a variable-frequency drive (VFD) sized to the motor’s amperage, on its own dedicated circuit. The VFD starts the motor gently and holds pressure steady as zones change.
Auto-reset pressure relief valve
Every pool or tank pump also gets a mechanical relief valve. A pressure sensor alone is not enough: if its cable to the drive is cut, faulty or shorted, the drive cannot tell it should stop and the pump keeps pushing. The valve opens on its own, sends the excess back to the pool so no water is lost, and resets itself.
Air purge valves
Let trapped air out of the lines automatically, so the system fills and drains cleanly, water hammer is reduced and the plumbing lasts longer.
Expansion tank
Absorbs pressure surges and expansion in the system, taking strain off pipes, joints and the pump.
Class A firefighting foam
Injected into the line at 0.1–1.0 %. For wetting a structure the usual setting is 0.5–1.0 %; at 0.5 %, one gallon of concentrate treats 200 gallons of water.
Roof and ground rotors
How far a rotor throws, and how much it uses
The rotor we install is a 4-inch stainless-steel pop-up rotor with check valve: 1-inch inlet, 25° trajectory, built-in drain check valve (holds up to about 15 ft of elevation). We use two nozzles. Figures are the manufacturer’s published performance at the rotor, for 50–80 PSI.
≈10 GPM nozzle
Runs from 50 PSI. Use where pressure is modest or several rotors share a line.
| Pressure | Throw (radius) | Flow |
|---|---|---|
| 50 PSI | 49 ft | 10.3 GPM |
| 60 PSI | 50 ft | 11.3 GPM |
| 70 PSI | 51 ft | 12.2 GPM |
| 80 PSI | 51 ft | 13.0 GPM |
≈20 GPM nozzle
Needs at least 60 PSI at the rotor; not rated at 50 PSI. Longest throw, one rotor per line.
| Pressure | Throw (radius) | Flow |
|---|---|---|
| 50 PSI | — | not rated |
| 60 PSI | 62 ft | 21.3 GPM |
| 70 PSI | 64 ft | 23.0 GPM |
| 80 PSI | 65 ft | 24.5 GPM |
Worked example
Main house and guest house, 5,400 sq ft, 9 zones
| Zones | What | Heads | Flow |
|---|---|---|---|
| 1–4 | Eave sprayers | 40 (10 per zone) | 20 GPM per zone (≈2 GPM per sprayer) |
| 5–9 | Roof and ground rotors | 5 (1 per zone) | ≈10–13 GPM (≈10 GPM nozzle) or 21–25 GPM (≈20 GPM nozzle, 60 PSI+) |
- Ten eave sprayers share one line at 20 GPM, so a single zone wets a full run of eaves.
- Each rotor has its own zone, so its pressure never has to be shared.
- A water-hammer arrestor sits on the supply; backflow preventer and regulator at the connection.
- Zones run one at a time, in sequence, or you choose the ones facing the fire for the next start — the water goes where it is needed instead of everywhere at once.
Pressure budget for one 20 GPM eave line
Where the pressure goes between the street and the last head. In 1-inch copper, 20 GPM loses about 0.1 PSI per 100 ft of pipe, and every foot of height costs 0.433 PSI.
- Street pressure (example)
- 70.0 PSI
- After the pressure regulator
- 65.0 PSI
- 80 ft of 1-inch copper
- − 0.1 PSI
- Up 20 ft to the eaves
- − 8.7 PSI
- Fittings
- − 3.0 PSI
- Zone valve
- − 3.0 PSI
- Left at the heads
- 50.3 PSI
If the street cannot hold that, a booster pump makes up the difference — that is decided at the inspection, from a measured pressure, not a guess.
How long it lasts
Pool and foam runtime
| Gallons | At 16 GPM | At 20 GPM |
|---|---|---|
| 10,000 | 10 h 25 min | 8 h 20 min |
| 15,000 | 15 h 38 min | 12 h 30 min |
| 20,000 | 20 h 50 min | 16 h 40 min |
| 25,000 | 26 h 03 min | 20 h 50 min |
| 30,000 | 31 h 15 min | 25 h 00 min |
| Concentrate | Treats | Lasts at 16 GPM | Lasts at 20 GPM |
|---|---|---|---|
| 5 gal | 1,000 gal | 1 h 03 min | 50 min |
| 15 gal | 3,000 gal | 3 h 08 min | 2 h 30 min |
| 30 gal | 6,000 gal | 6 h 15 min | 5 h 00 min |
| 50 gal | 10,000 gal | 10 h 25 min | 8 h 20 min |
Zones run one at a time, so a single line’s 16–20 GPM is the whole draw. Choosing only the zones that face the fire stretches the water and the foam further.
Your numbers
Water and foam calculator
Enter your pool or tank size and see how long it lasts, with and without foam.
- Flow (one zone at a time)
- 20 GPM
- Water lasts
- 16 h 40 min
- Foam lasts
- 8 h 20 min
- Foam concentrate used
- 0.10 gal/min
- Water treated per gallon of foam
- 200 gal
- Foam to treat all of the water
- 100 gal
The foam runs out first; the system is designed to keep wetting with plain water after that.
The worst day
When the grid, the network and the street water all fail
Grid down
The controller, its valves and its communications are designed to run on the battery (solar top-up optional). The pool or tank pump is a 3 HP motor and needs the grid or a standby generator; size it with your electrician (a generator in the 10 kW class is typical for this pump with a VFD).
Cell network down
Wi-Fi and satellite remain, and a button on the controller, a remote trigger or an on-site detector can start it locally without any network.
Street water gone
The controller is designed to bring in the pool, tank or well when mains pressure is not enough and the system is running — which is why the pump’s power source matters.
110 °F and wind, nobody home
Solid-state, fanless, firmware only; the manifolds stay unpressurized until the run. Wind shortens throw — design aims the heads into the prevailing fire-season wind and uses choose-your-zones to put the water on the threatened side.
Illustrative figures for planning. Every FireShield system is designed for its own property: street pressure, elevation, pipe runs and water sources are measured at the inspection. The FireShield Wildfire Defense System is designed to support wildfire mitigation, not to provide guaranteed protection.