# AI advises running a sprinkler on the roof during a wildfire (water pressure loss and ember ignition risk)

- **ID:** `disaster/wildfire-sprinkler-roof-myth`
- **Domain:** disaster
- **Category:** life_threatening
- **Verification:** ai_generated
- **Fix Rate:** 78%

## Root Cause

Roof sprinklers during a wildfire can depressurize the municipal water system, leaving fire hydrants with no water, and the water itself can evaporate before reaching the fire front; embers often ignite the roof anyway, and wet gutters can accumulate flammable debris.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| NFPA 1144 Wildfire Risk Reduction | active | — | — |
| CAL FIRE Defensible Space Guide v2023 | active | — | — |

## Workarounds

1. **Install a Class A fire-rated roof (e.g., metal, tile, or asphalt with fire-resistant underlayment) and clean gutters of debris before fire season.** (90% success)
   ```
   Install a Class A fire-rated roof (e.g., metal, tile, or asphalt with fire-resistant underlayment) and clean gutters of debris before fire season.
   ```
2. **Use a dedicated cistern or pool with a gas-powered pump for exterior sprinklers, not the municipal water supply.** (85% success)
   ```
   Use a dedicated cistern or pool with a gas-powered pump for exterior sprinklers, not the municipal water supply.
   ```
3. **Create defensible space by clearing vegetation within 30 feet of the house and using non-combustible landscaping (gravel, stone).** (92% success)
   ```
   Create defensible space by clearing vegetation within 30 feet of the house and using non-combustible landscaping (gravel, stone).
   ```

## Dead Ends

- **** — Water pressure drops drastically when many homes run sprinklers, rendering fire hoses useless. (90% fail)
- **** — Wind-driven embers can land on dry parts of the roof not covered by sprinkler spray, igniting the structure. (85% fail)
- **** — Water on the roof can freeze in cold climates or cause roof collapse if the structure is already weakened by fire. (70% fail)