How Much Rainwater Does A Roof Collect

Take the dimensions of the footprint of your roof and convert them to inches.

How much rainwater does a roof collect.

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. Annual rainfall in millimetres x roof surface area in square metres roof catchment capacity. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l.

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. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember. Rain barrel supplies list. Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water.

To find how much rain you can collect in an average rain year multiply this number by the average inches of rain. 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. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. The collectable rainwater from the roof can be calculated in gallons using this calculator based on the rainfall and area.

To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. When you look at the numbers it s surprising how much water you can collect every time it rains. Keep in mind most rain falls over 2 3 months of a year. 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.

Rainwater can be collected from the roofs using the rain water harvesting method. This capacity can be calculated using the following formula. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water. So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall.

1 of rain on 1 000 sf roof will yield 623 gallons roof area m2 x precipitation amount mm amount collected liters other water conservation calculators. That s 600 less gallons you have to pay for and use from your town water supply.