The short version
- On the day a fire comes, you may not be home, and the power and internet may be out. The system has to do everything on its own.
- FireShield's protection works in four stages, and each one has to lead correctly into the next: waiting, deciding to start, running, shutting down.
- Spraying water is the easy part. The hard part is sitting idle for years and then working when it's needed.
- Most of FireShield's design assumes nobody is home: there's no fan to fail, it can run without the internet, and it doesn't need anyone to press a button.
- If you're comparing systems, ask each company to walk you through all four stages, not just the spraying.
Most wildfire system demos show the same thing: someone taps a phone and water comes off the roof.
That's the easy part. Below is everything else that has to go right, in order.
Waiting between fires
Your system spends almost all of its life waiting, and this is where problems can go unnoticed.
The pipes stay empty. A valve at the water supply stays closed, so the pipes on your walls and roof aren't under pressure when the system isn't running.
Pipes under constant pressure wear out faster and can leak. Keeping them empty avoids that.
If something breaks, the water stays off. The supply valve is normally closed, so if a wire is cut or the controller fails, the water shuts off. A utility power outage is different: the controller and the valves keep running on built-in backup power. FireShield's patent gives the reason directly: it protects against "runaway water use, water cost, and flooding of an unattended structure."
Nothing is wearing out. There's no cooling fan, no vents and no filter to service. There's a separate article on this.
It checks in. FireShield reports to its servers regularly, so someone knows it's online and working.
Deciding to start
When a fire starts somewhere, FireShield has to decide whether your house is in danger.
From fire data. FireShield's servers collect fire data from several sources and work out how far the nearest edge of each fire is from your house.
What starts it. Your house has an activation distance, which is how close a fire has to get, and a delay, which is how long the system waits after that before it starts. When the nearest edge of a fire comes within the activation distance, the delay counts down, and then the system starts. Your technician sets both at installation, typically starting from 6 miles and 9 minutes, and you can cancel during the countdown.
From the property itself. There's a button on the FireShield controller, a wireless button you can press on your way out, and heat, smoke, flame or camera sensors wired to the controller.
However it starts, the system responds the same way. Three of the four ways need no internet: the controller's button, the wireless button and on-site sensors.
What happens while it runs
Once the start command arrives, here is what happens, step by step.
First, it records what it's about to do. This lets it pick up where it left off if anything interrupts it.
It opens the water supply and checks the pressure.
It runs a few zones at a time. No house has enough water to run every sprinkler at once, so FireShield runs as many zones together as the water pressure can support.
It switches zones gently. It opens the next valve before closing the last one, which protects the pipes.
It times each valve separately. Each valve gets the right amount of time to open fully, from its settings.
If water pressure runs low, it uses your pool. When the pressure drops too low while the system is running, FireShield starts your pool pump to push more water. Both have to be true, so a pressure dip on an ordinary day never touches your pool.
If the power goes out, it keeps going. The controller and the valves keep running on built-in backup power. The pool pump needs electricity, so it needs its own backup power option or a generator; without one, it will not run during an outage. If there is a generator, FireShield runs it only when the system is active and utility power is gone, not for brief flickers in the power.
It runs every zone, unless you choose otherwise. By default every zone runs automatically. If you want, you can favor certain zones or turn some off in the app, so limited water goes where you choose.
If something resets, it picks up where it left off. That could be a brownout or the watchdog circuit restarting the software. FireShield reads the record it wrote in step one, drives every valve to its correct position, and resumes from the exact zone it was on — "without re-establishing communication with a remote backend." It doesn't need to check with anyone first. There's more on this in What Happens When the Cell Towers Go Down.
You can choose to keep the water on. If the backup power ever runs out, the supply valve closes to protect an empty house from flooding. If you'd rather keep the water flowing, you can tell FireShield ahead of time or during the event.
Shutting down after the fire
After the fire, the system gets itself ready for next time.
It drains the pipes. FireShield empties the pipes through a drain line, so no water is left sitting in the lines on your roof.
It can flush the lines. If foam was used, FireShield can run plain water through to clear residue out of the nozzles. Otherwise, dried foam residue is what clogs sprinkler heads between events.
Then it drains again.
It closes the supply and goes back to standby. The pipes are empty again, and FireShield records the event.
Then it goes back to waiting.
Why it all has to work together
Spraying water is the easy part. Most of the design is built around the fact that nobody will be home.
There's no fan because nobody will be around to service it. The pipes stay empty because nobody would notice a slow leak. There are several ways to start it, so it doesn't depend on any one of them. And it shuts itself down and drains the lines on its own.
FireShield's patent makes the argument directly, and it's the honest version: no single one of these features produces the result. The controller reading its settings at runtime is what lets one controller handle any property. That same awareness of every zone is what makes pressure-correct sequencing possible. The two-condition interlock is what lets a limited pool be used without being wasted. Isolation that closes by default is what helps keep an empty house safe. Its memory is what carries a run through a blackout.
What to ask before you sign
| Question | Why it matters |
|---|---|
| Are the pipes pressurized while it's idle? | FireShield keeps its pipes empty in standby. Constant pressure wears on the joints over the years. |
| What happens if it loses power mid-run? | FireShield's controller and valves keep running on built-in backup power, and after any reset it resumes the sequence from where it stopped. The pool pump needs its own backup power option or a generator. |
| How many ways can it start without internet? | FireShield has three. |
| When does it draw from my pool? | Only on low pressure and an active run, never on an ordinary day. |
| What does it do after it finishes? | FireShield drains the pipes, flushes them if foam was used, drains again and closes the supply. |
Ask any company you're considering, including FireShield, to walk you through all four stages.
On the day this matters, you may not be home. Everything above has to happen without you, and that's what FireShield is built to do.
Next in this series
- Why Wildfire Controllers Fail on the Hottest Day — The cooling fan and the computer, and why FireShield has neither.
- The Setting You Can Change in Ten Seconds — How the settings fit the system to your house.
- What Happens When the Cell Towers Go Down — The four ways to start it, and what keeps working in a blackout.
- Skip the Zones You Don't Need — Watering only part of your property when you choose to.
About FireShield — FireShield builds automated exterior wildfire defense systems for homes across Southern California. The system described here is covered by FireShield's patent. See the wildfire defense system or talk to us.