How much water can I collect from my roof?
With unreliable or reduced waterfall, water restrictions, bans on sprinklers and even hoses many people give up on the idea of trying to grow vegetables. It uses just too much valuable water. We need to understand though, that we all have a large or even huge water resource above our heads, often quite literally going down the drain in urban areas.
If you don’t already have a water tank read on, if you do - are you using it to its maximum potential benefit?
So how much water does your roof collect?
There is a very simple formula you can use to calculate your average water collection potential.
First measure the length (L) and width (W) of your house, don’t worry about the roof slope it doesn’t count.
Next find out your average annual rainfall, the weather bureau has a figure for this, or better still, buy a rain gauge and record your own results.
The formula is:
(L x W x rainfall in mm)x.8 = Kilolitres collected
1000
The result is how many Kilolitres you could have collected. The .8 factor is to correct for losses as not all water will make it to the tank. I have included a simple excel based calculator for you to make it easy.
You will find you have more than enough water for the garden, washing the car and even flushing the toilets in most major Australian cities. Here on our property, all our domestic water needs come from our roof. We don’t manage to collect it all as the tanks regularly overflow. It is a great feeling to be water independent.
When collecting water from your roof surface, be aware that some roof materials are not suitable for collection of drinking water. You will also need to be aware of council conditions and restrictions on the use of water tanks. If you find these conditions and restrictions prohibitive, now is the time to get together with your fellow residents and petition for easier access to self water collection.
