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There are a number of ways to look at How Much Water Storage you require but the answer must that you have enough Water Storage to cover you for the longest dry period which could be 60 to 90 days depending on where you live

So the amount of Water Storage you require is Litres used per day * days without good rainfall

Every household is different depending on the number of people in the house, how they use the water, number of appliances, bathrooms use of water outdoor for gardens, pool and washing cars etc

Based on our experience a normal household (3-4) people use between 500 & 750 litres per day.

Therefore based on the above a household needs at least 40 - 50,000 litres of water storage which equals to 2 water tanks of 25,000 litres or 30,000 litres each.

The table below sets possible water use and storage requirements.

Days is the the number of days between significant rainfall. Remember it can rain without having much effect on tank water level. 

(On 100 sq metre roof you need 10mm of Rainfall to add 1,000 litres to your tank.) 

Daily Water
Usage (Litres)
30 Days60 Days90 Days

Water is extremely precise as we cannot live without it. Climate Change is affecting rainfall and natural disasters so the amount of water you store is extremely important. Therefore we recommend that you install the greatest volume of water storage that room & budget allows (remember you can always added additional tanks at a later time if you have a contingent plan). The extra cost of bigger or more tanks is minimal compared to the cost of installation and plumbing requirements.

We are Rainline are here to help so if you have any questions or require more information please contact us


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