How Much Rainwater Does A Roof Collect

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.

How much rainwater does a roof collect.

Take the dimensions of the footprint of your roof and convert them to inches. 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. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. Rain barrel supplies list.

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

The collectable rainwater from the roof can be calculated in gallons using this calculator based on the rainfall and area. Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water. So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall. When you look at the numbers it s surprising how much water you can collect every time it rains.

That s 600 less gallons you have to pay for and use from your town water supply. 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. Rainwater collection calculator in gallons. 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.

If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. Rainwater can be collected from the roofs using the rain water harvesting method. Keep in mind most rain falls over 2 3 months of a year. 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.

For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. This capacity can be calculated using the following formula.