How Much Rainwater Does A Roof Collect

Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water.

How much rainwater does a roof collect.

Rainwater collection calculator in gallons. The collected rain must be used on the property where it is collected and may only be used for outdoor purposes such as lawn irrigation and gardening. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.

An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. Keep in mind most rain falls over 2 3 months of a year. The collectable rainwater from the roof can be calculated in gallons using this calculator based on the rainfall and area.

To find how much rain you can collect in an average rain year multiply this number by the average inches of rain. Annual rainfall in millimetres x roof surface area in square metres roof catchment capacity. This capacity can be calculated using the following formula. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember.

When you look at the numbers it s surprising how much water you can collect every time it rains. Rainwater can be collected from the roofs using the rain water harvesting method. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. Rain barrel supplies list.

In 2016 house bill 16 1005 was passed allowing residents to collect rainwater from a catchment system on their rooftops into two rain barrels with a combined capacity of 110 gallons. That s 600 less gallons you have to pay for and use from your town water supply. If you have 1 000 square feet of roof on your house and it rains just 1 inch you can collect 600 gallons of water to be used in your garden for washing your car or just for drop irrigation around your property. So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.

A one inch rain will collect 600 gallonsfrom a 1 000 square foot roof while 4 500 square foot lot will receive 2 800 gallons. In this example 600 x 240 x 1 144 000 cubic inches of water divide by 231 to get the number of gallons because 1 gallon 231 cubic inches.