STEP 1: Determine the size in litres of the tank that you need.
Work out your roof catchment area that will be used to fill the rain water tank. Once you figure out the roof area, use this simple calculation you can determine how much water you will collect per average annual rainfall. For every 1mm of rain falling on a 1m2area of roof will be approximately 0.9 Litres.
0.9 x Average Rain Fall In mm x Square Meters Of Roof
(e.g. 0.9 x 1200mm x 150 = 162000 Litres per year)
Next work out what you will use the water tank water for e.g. flushing toilets, washing machine, and garden taps etc. You then can use the following table to calculate your daily rainwater demand.
One flush of a dual flush toilet
One load in a standard washing machine
Washing of an average size car
Hosing of a driveway
Standard garden sprinkler
Drip style sprinkler
e.g. The tank water is going to be used to flush two toilets (at an average of 12 flushes each a day) and one load of washing per day. Add to these washing two cars once a week and a drip sprinkler ran for 2 hours twice a week. In one week the demand would be 2,678 Litres.
STEP 2: Determine where you want to locate the tank.
Find the most appropriate area in your yard for the water tank. Take into account that you need to run a downpipe to fill the tank, it’s not going to impeded access down the side of the house and local council guidelines. Now measure the designated area that you want to situate your rainwater tank.
STEP 3: Calculate which water tank is best for you.
Using all your previous measurements and calculations you can now decide on a tank from our extensive range which is best suited to your needs.
E.g. You have a space down the side of your house that is 1200mm wide and 5000mm long with a space 3000mm to your eaves. You could fit a 5000Litre slimline water tank that is 825mm wide x 4075mm long x 2180 high. This would give you approximately one and a half weeks of rainwater to use if the rainwater tank was full.
If you are using the tank water for toilet flushing etc, a Davey Rain Bank Switch is recommended. This will automatically switch over to mains water supply for flushing of the toilets and washing machine when the tank level drops too low. If the tank water is only going to be used to water the garden and wash cars etc a standard pump can be used.