Water Storage Tank

There is no question about it – the issue of water costs is not going to go away and maybe the best way to fight the water charges is to come up with ways in which we can store of own water and save on any water charges or bills


There are many ways in which we can store water and depending on the size of your home or business there is a water storage tank to suit your roof size.

Working Out The Right Size of Tank

An average home has a roof size of 75m2 and this rainwater catchment area could harvest about 50m3 of water each year. This is assuming an average rainfall of 1000mm which is typical for Ireland

50m3 is equal to 50,000 litres of water. Of course, you won’t need to store a full year’s harvest at one time – as you will be continually using the water from the water storage tank each day. The average annual water consumption per person is said to be around 50,000 litres! Of course not all your water needs can be met from water storage tanks

Water storage tank usage:

Connecting your water tank to your attic tank will allow you to:

  • Flush toilets: 27%
  • Garden: 12%
  • Washing clothes: 10%

The rest: 51% – The rest would require a filtered, potable water system.

But as you can see, 49% of the water you use can come from your water storage tank, That means 25,000 Litres of stored water can be used annually per person. This equates to about 70 Litres each day from a storage tank needed per person to fulfil their needs. But because of sporadic rainfall we should assume a week supply at any one time and we then should add the number of people per house, say 3 for this example.

This would suggest that an average sized house, with 3 people living in it should choose a water storage tank of:

70L  x 7Days x 3People =  1470 Litre water storage tank

This, when full would have enough water for one weeks showers, toilets & garden use. Then, so long as rainfall is regular and there is no long drought, the tank should refill in that time to provide further water supply

This assumes that in a week, you roof would need to receive 1470 Litres of water. Thats 19mm of rain fall per week, which is the annual average – but in the summer months this would be lower where it can drop do to approx 15mm per week.

But all said, this can show that a water storage tank of 1470L would be very close to meeting 50% of the water needs on an average sized family, in an average sized house in an average years rain fall