How much rain can you collect from your roof?

So you want to learn more about collecting rainwater? That’s great – you’ve come to the right place. Australian homeowners are savvier about their lifestyle choices and sustainability is a popular trend.

If you’re interested in increasing the sustainability of your home or building a home and looking for ways to hit your 6-star rating by utilising a rainwater tank here’s some useful information on how much rain you can collect from your roof.

How do you catch rain to collect it?

When rain falls on your roof the angle of your tiles/steel sheets direct the water towards your gutters. The water is then sent through the down pipes and into the sewer. A reminder that it’s essential to keep your gutters clean, otherwise that water won’t escape into the sewer, but through your roof and into your home.

What if, instead of sending your water to the sewers you collected it and kept it for later use? Now you’re talking about rainwater harvesting.

Angled tiles for sending rain to gutter

What are the advantages of collecting rainwater from my roof

The advantages of collecting rainwater, or rainwater harvesting are:

  1. Flushing toilets
  2. Water for irrigation around your property
  3. Water for any plants/vegetables you’re growing
  4. Stored water can be used during droughts
  5. Stored water can be used during especially hot days without increasing your water bill
  6. It’s beneficial for the environment

You’ll have lived through some scorching Oz summers and sometimes our lawns and plants just can’t keep up. With harvested rainwater you can keep the plants watered throughout the harsh conditions, guilt-free as you supplied the water, it hasn’t come from the mains.

How do I calculate how much rain my roof can collect?

Let’s get to the point – you came here to find out how much rainwater can be collected from a roof and here’s how you work it out:

  1. Find the square metres of your home
    Length of your home x width of your home = square metres (m2)
    (the slope of your roof doesn’t affect this figure and if you have a few roof sections do this for each section and add them together)
  2. Google rainfall for your area (mm) x your roof surface area (m2)
  3. The answer = the amount of rain you can collect from your roof in litres

For example:
If you live in Melbourne, your average annual rainfall is 648mm (according to BOM).
The average roof size is 200m2
648×200 = 129,600L

tank for collecting rain from a roof

What size water tank do I need to collect rain from my roof?

If you live in Melbourne and assume that you’re going to collect 129,600L or rainwater over a year you might assume you need one giant, house-sized tank to collect it all. But bear in mind that some months rain more than others and you’re not going to need to store 130,000L of water all at once.

Across Victoria new buildings are required to install a 2,000-litre water tank to reduce the strain on the water system as the population size of Victoria grows. A 2,000-litre water tank should suffice to meet the average homeowners needs for greywater.

So, if you’re wondering how much rain you can collect from your roof and you live in Victoria? The answer is about 130,000litres a year.

We hope that you got some value from this guide. If you want a gutter cleaning professional service provider in Melbourne to inspect your roof and clean the gutters, contact PorterVac today.

What are the advantages of collecting rainwater from my roof?

Flushing toilets, irrigation around your property, stored water can be used during droughts and on hot days and it’s beneficial for the environment.

How do I calculate how much rain my roof can collect?

The amount of annual rainfall for your area (mm) x your roof surface area (m2)

What size water tank do I need to collect rain from my roof?

New Victorian homes are required to install a 2,000-litre water tank and this will be sufficient size for the average home in the state.

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