If you live in Australia, the question isn’t whether you need a water tank … it’s what size. A number of factors influence this. One is the size of your family. The more members your household contains, the larger your water storage capacity should be. You could also consider the climate. Most of Australia has an annual monsoon season, but some regions have more frequent precipitation and even a little snow.
You should also consider what you’re using the water for. Rain water isn’t generally used for cleaning unless you chemically treat it first, so maybe it’s just for the toilets and general cleaning. If you have a flower garden or an active farm, you probably need bigger tanks. The easiest way to figure out your usage is with an online calculator.
These free pieces of software can give you a reasonable estimate of how much water you consume in a week, month, or year. Input your preferred usage of water and how many people you live with. For example, an average shower uses up 10 litres per minute per person, and a family washing machine uses up over 100 litres in every load.
Household estimates for water use
If you have a pool, you lose about 12 cm of water a day, depending on the size of your pool. When you run the tap to wash your hands or brush your teeth in a sink, you use 5 litres per minute. Most people take two minutes for both, so that’s 10 litres. That’s why it’s a good idea to close the tap while you’re applying the soap or toothpaste.
Australian reports imply that a household can use about 20,000 litres in a month. The average person uses 10 litres of water a day for their drinking, cooking, and cleaning needs. Other interpretations put the number as high as 300 litres a day, including their showers, laundry, and other uses. Here are a few more estimates.
- 8-minute shower: 80 litres
- Bubble-bath: 150 litres for a full tub
- Laundry: 80 to 100 litres per machine load
- Kitchen/bathroom sink: 5 litres a minute
- Brushing your teeth: 10 litres
- Flushing the toilet: 3 to 6 litres per flush
- Garden water pipe: 15 litres a minute
- Drip irrigation system: 6 litres per hour
- Washing your car: 200 litres per wash
What’s your largest water-use category?
We’ve talked about the specific ways water is used in your home, but there are also general patterns that can be used to determine water use. For example, as sexist as it sounds, a house with more women (or teenagers of any gender) are likely to use more water. Think long showers and soothing baths.
A house with many drivers will obviously use more, especially if everyone has their own car. And obviously, agricultural households, gardeners, and pet lovers need bigger tanks. Decorative aquariums consume a lot more water than you’d think, especially if you’re diligent about your fish hygiene.
If you’re specifically an in ground rain water tank, you’re looking to do one (or more) of the following:
- Avoid flooding
- Store water for gardening or farming
- Collect water for household use
- Reduce reliance on municipal mains
- Replace government water sources
The last option may be dependent on cutting costs, or it may be a vital way of life in areas where municipally piped water is unavailable. Your primary water goal directly influences the size of your tank. The most popular tank size in Australia is 22,000 to 24,000 litres, but your selection may depend on your home layout. Underground tanks can be quite large, but if your surface is loose, and concrete slabbing is too expensive and labour-intensive, you may opt for several smaller tanks that add up to your preferred capacity.
When it rains, your gutters can overflow and flood your yard. An onsite detention tank (ODT), or a detention control pit (DCP) of 720 litres to 3,000 litres can temporarily hold flood water when it rains. If you have a single gutter, use 720 litres to 1,500 litres, with the 3,000 litre option for multiple down pipes.
The water will gradually and safely be transferred to the city sewer or channelled into a larger rainwater tank. The reduction in the rate and volume out-flowing water will prevent overwhelming the public storm-water drainage system. If you intend to guide rain water into your garden, you can buy a plastic tank that’s anywhere from 300 litres to 3,000 litres.
If you prefer a corrugated tank, they can go 7,600 litres to 250 kilolitres, which can probably collect water throughout the rainy season before filling up. For home use, your drinking water tank can be 500 litres to 1,500 litres, while your general cleaning and hot water tank can be 3,000 litres to 6,000 litres.
Finally, if rain water is your only water source, you need a plumbing system that uses the entire roof for water catchment. This maximises the amount of water you can harvest. Your tank capacity will have to total 130 kilolitres to 160 kilolitres. This can be distributed between concrete in-ground tanks and corrugated metal or polyethylene surface tanks.