External Water Spray System

Caution: I’m no expert. These articles give my opinions and beliefs that may all be wrong. An EWSS is to protect your home and life; you need to make up your own mind. It is your risk.

A home Wikipedia article External Water Spray System (EWSS) is a system of sprays located on and around a home to help protect it from a bushfire (wildfire).

While throwing a lot of water out around a home has got to help, an EWSS is not a substitute for active defence of your home as:

  • There has been little or no research on these systems and current practices are based on best guess or current industry practice.
  • While many systems are installed, few if any (I guess), have actually been proven in a real fire situation.
  • It would be difficult to defend a home remotely with EWSS as it may not be possible to provide enough water to sustain the system during an ember attack lasting last many hours.

The only article that I know of that studies EWSS is one published by the Fire Protection Association Australia (FPAA). A summary can be downloaded from here. The FPAA can email you the original.

Our System


The FPAA publication I mentioned above mentions a three zone approach of:

  • Inner - Sprays directed towards home walls and/or windows.
  • Mid – Butterfly sprays providing a curtain around the home of high humidity, and wet down immediate surrounding area.
  • Outer – impact sprays wetting down surrounding bush.

This does seem to a common language in the industry so I will use it to describe our system and my thinking. The dogs run sprays however do not quite fit into this model and are described as a fourth zone.

Dog Run

Our dog run is about 30 meters from the house and is where our dogs are when we are at work. It is about 20 meters longs and 10 meters wide. What we want is to be able to keep the area wet during a fire so that a surface spot fires that may be started by embers cannot run through the run. This is the primary objective of our remote start EWSS system.


Inner Zone


Mid Zone


Outer Zone



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