The pressure you will have in your Ember Defender system will vary depending on how many sprinklers you have connected, the height of your roof, and water pressure from your tank or mains supply. Also, in a bushfire situation you need to assume the worst and allow for lower water pressure than what is normally available from your mains supply. The butterfly sprinkler head used on the Ember Defender unit is specifically designed to maximise water coverage at low water pressure. To achieve maximum water coverage on your roof from your Ember Defender units, the water pressure should be around 150 kPa, 21.7 psi or 15.3 metres head.
If you are using tank water, most pumps will provide more than adequate water pressure as they normally operate above 350kPa. If you are using mains water, again water pressure is usually adequate. For example while Sydney Water guarantee water pressure of 15 metres head or 147kPa, on average water pressure is 50 metre head or 490kPa. Even if this is reduced by 60% the average water pressure would be 20 metre head or 196 kPa.
Also, if you are running off tank water you need to understand how long you can run the system for (assuming you lose the water and it doesn’t run back into your tank!)
It is estimated that 1 to 1.5 million homes are located within 130m of bushland, classifying them as being located in a bushfire prone area. This estimate is based on the following information.
In 2005 there were over 10.9 million known addresses in Australia of which 80%, or 8.3 million homes, are located in major capital cities and their surrounding areas. Of those 8.3 million homes, 338,000 are located within 80m of bushland and 489,000 are located within 130m of bushland.
Source: COUNTING BUSHFIRE-PRONE ADDRESSES IN THE GREATER SYDNEY REGION, Keping Chen, Risk Frontiers - Natural Hazards Research Centre, Macquarie University, 2005
Of the remaining 2.6 million located in rural areas it is not know what % are located within 80m or 130m of bushland. If we assume 50% of these homes are in bushfire prone areas (give or take 20%) then we get a range of 1.040 million to 1.560 million.
An article published by The Sydney Morning Herald, suggests that as many as 1 million homes in Sydney alone face a serious risk from bushfires.
The Ember Defender system is designed to reduce the impact of ember attacks on your home in the case of a bushfire. It is not designed to protect your home from radiant heat or direct flame in the case of a bushfire.
This will depend on the shape and area of your roof. For a standard roof size of 250m2 you would require 3 units to provide adequate coverage. For unusual shape rooves or larger houses you may require more.