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How to Calculate Your Home Water Usage

Earth’s surface is two-thirds water, 71% to be exact, and of that around 2.5% is fresh water. With such limited fresh water supply, governments invest in desalination plants, recycled water, dams, underground water sources and like. Supplying fresh water on demand is a costly exercise, but a basic requirement for developing societies.How to Calculate your Home Water Usage

In Australia, property owners pay to tap into the government’s “mains water” supply. It is quite easy to determine our water usage, because the amount of our water usage is normally included with council rates or water utility notice. If our water usage wasn’t tracked however by government, then would we be able to estimate our water usage? The aim of this article as the title says, is to help you calculate the amount of water required by your home.

Clark Tanks provide an online water usage calculator that home owners like yourself can use to help estimate water usage, inside and outside water use. There are several areas in the home where water is regularly consumed. Water usage can be broken up according to routine household activities.

Bathroom Water Usage

When you wake up in the morning the first point of call is normally the toilet and bathroom. Bathroom habits and frequency varies per individual, so you will need to perform some estimates for your own use as well as the usage of others in your house.  Here are some domestic water usage estimates per use:

  • Shower
    • water saving shower head: 10 litres per minute
    • full water flow: 20 litres per minute
    • unsure? 15 litres per minute
  • Bath: 150 litres
  • Toilet:
    • full flush: 6 litres
    • half flush: 3 litres
  • Basin (washing hands, brushing teeth): 5 litres per minute

Kitchen Water Usage

After relieving yourself, washing hands and/or showering, you likely make your way to the kitchen for breakfast. The kitchen is the other area where water is obviously consumed for use in cooking, drinking purposes and washing of hands and dishes.

  • Drinking, cleaning and cooking: 10 litre each day per person
  • Dish washing:
    • Inefficient machine: 30 litres per full load
    • Efficient machine: 15 litres per full load
    • Human hand washing: 10 litres per person

Laundry Water Usage

The other area where water is routine used is in the laundry. Clothes, even in the smallest families, build up quickly. Depending upon clothes habits, diapers (if you dislike disposables), how regularly bedsheets and towels are changes and the like, small families can have a load every one to two days and larger families one to two loads per day.

  • Washing Machine
    • Front loader: 80 litres per load
    • Top loader: 100 litres per load

Outdoor Water Usage

In the above we have just been describing indoor water usage, but what about outdoor usages when washing pets, your car, topping up your swimming pool, garden usage and the like? Here are some calculations you can use to estimate your outdoor water use.

  • Hosing (garden, surfaces): 15 litres per minute
  • Drip water system: 6 litres per hour
  • Car washing: 100-200 litres
  • Dog or pet: 50 litres per wash

Total Household Water Usage

Now we have some figures to work with, you just need to calculate your house hold usage. How many people are in your home, how many cars need washing, do you have a swimming pool, lush gardens, a lawn, hard surfaces that need washing down and the like. This will give you a reasonable calculation of your properties water usage requirements.

After calculating out how much water is consumed in your home, obviously only so much rainwater falls from the sky and it falls at different rates. You can find out how much water falls in your area on the Australian Government Bureau of Meteorology website.

Recommended Tank Sizes

Calculating can obviously get quickly complicated and is time consuming. So if you prefer to take a shortcut, then according to YourHome, a minimum tank capacity of 5,000 litres is to 20,000 litres is recommended. That is, to supply water to a four-person household, that still has access to mains water and fairly even spread of rainfall.

As a point of note, Clark Tanks’ most popular rainwater tanks are our traditional-look corrugated round 5,000 gallon (22,700 litre). This tank size obviously fulfills YourHome’s maximum recommendations. So provided you have room on your property, then this would be an ideal size tank for most residential properties.


Download – How to Calculate your Home Water Usage