What Size Rainwater Tank Should I Install?


When it comes to installing a rainwater tank, one of the most frequent question people ask is how to choose the best size. It’s an important question to ask since the choosing the right size will mean a tank that will work best for your needs and save you money. On the other side of the equation an inadequate sized tank could cost you more money that you realise, and the wrong size could also lead to water supply issues.

The Tank Specialists can provide the right advice to guide you in this very important decision. We explain some of the major considerations when selecting a rainwater tank below. 

How the Water Will Be Used

For properties not connected to mains water a water tank with a capacity large enough to provide enough water for the number of people in the household will be needed. A larger family will need a tank at least large enough for all household water activities including washing machines, showering and gardening. However if you are looking at a supplementary water source for external use around the home including washing cars and watering the garden, a smaller tank for external use only may be sufficient.

The Average Rainfall in your Area

The more rainfall an area receives, the less important it will be to have a larger tank. However we still recommend having a size with the capacity to store extra water for dry periods.

The Size of Your Catchment Area

For each square metre of roof, one litre of water will be collected for every millimetre of rainfall. If the average size roof of the home is 160 square metres, the area of the roof that can be connected to the tank may be 50 per cent of the roof – 80 sq m. For 10mm of rain, the tank would collect 800L of water. The larger the areas of the roof that can collect water for the tank the better

The Space Available for the Tank

As a general rule we recommend the largest size tank that you can afford and have space for. This will provide enough water during droughts and long dry spells. However in some homes the amount of space will be limited so there may need to be some compromise on the size of the tank, or investigation of different options including underground, or a tank that can be concealed under a veranda or deck.

An Example of Water Usage for a Family of Four

With the average household using around 200L of water per day per person, a rural property in a drier area of Queensland that is not connected to mains water supply with 4 occupants will use 800L, a 92,570L tank will provide sufficient water supply for 115 days with no rain.

It’s also a good idea to realistically assess the water usage habits of your family to understand what size tank will be best for your needs.

The Tank Specialists can help you understand what size tank you are likely to use, and we won’t try to oversell you – depending on the individual situation and the needs of your household will allow us to recommend a tank size that will work for your home and budget.

Call us today on (07) 4974 7333 for more advice about installing a rainwater tank in Hervey Bay, the Sunshine Coast, Bundaberg and other areas of Central and Southeast Queensland.

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