How Much Rainwater Does My Roof Collect

If you can try to use a billboard tarp which is around 20 in 30 in 51 cm 76 cm in size to collect as much rainwater as you can.

How much rainwater does my roof collect.

Annual rainfall in millimetres x roof surface area in square metres roof catchment capacity. Gallons collected per inch of rainfall 0 62 total collecting area of roof in square feet so if you have a 1 000 square foot house you can potentially collect 0 62 1 000 620 gallons of water every time it rains an inch. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above. To find how much rain you can collect in an average rain year multiply this number by the average inches of rain.

You can use a tarp of any size to collect rainwater but a larger the surface area the more water you ll harvest. 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. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. That s 600 less gallons you have to pay for and use from your town water supply.

If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. This capacity can be calculated using the following formula. 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.

When you look at the numbers it s surprising how much water you can collect every time it rains. 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. An average suburban roof of 200m 2 with such a rain fall can potentially harvest 100 000l of rainwater 200m 2 500mm 100 000l. Keep in mind most rain falls over 2 3 months of a year.

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. 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. With two inches of rain you can collect around 1 240 gallons. You can use the precipitation map below to find an approximate amount for your area.

Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water. So how can you do the math for your own roof. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water. 1 of rainfall over 1 000 sf will yield 623 gallons to calculate the amount of rainwater you can collect you need to know your annual average precipitation for your area.