How Much Rain Water Will Roof Collect

Roof area m2 x precipitation amount mm amount collected liters.

How much rain water will roof collect.

To find how much rain you can collect in an average rain year multiply this number by the average inches of rain. Rainwater can be collected from the roofs using the rain water harvesting method. Collected rainwater may be used to irrigate outdoor lawns plants or gardens. Most states have shifted their laws in favor of private rainwater harvesting.

Take the dimensions of the footprint of your roof and convert them to inches. The collectable rainwater from the roof can be calculated in gallons using this calculator based on the rainfall and area. If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. Untreated rainwater collected from roofs is not safe to drink.

Colorado the state with arguably the strictest rainwater harvesting laws passed a bill in 2016 allowing for the collection of rainwater with a 110 gallon maximum capacity. So a 50 x 20 roof is 600 x 240 multiply the roof dimensions by the number of inches of rainfall. Keep in mind most rain falls over 2 3 months of a year. Rainwater collection calculation formulas and equations.

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. To comply with colorado water law the container must be equipped with a sealable lid. 1 of rain on 1 000 sf roof will yield 623 gallons. Just a half inch of rain falling on a 1 000 square foot roof will yield 300 gallons of water.

When you look at the numbers it s surprising how much water you can collect every time it rains. It isn t uncommon for an area to collect up to 350mm of rain in just one month even in rural areas. Traditionally this involves harvesting the rain from a roof. The rain will collect in gutters that channel the water into downspouts and then into some sort of storage vessel.

To calculate the runoff from any given rainfall. Any container capable of collecting the rain shedding from a roof or patio can be used as a rainwater harvesting system. Rainwater collection calculator in gallons. To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above.

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. Roof area ft2 x precipitation amount in x 0 623 amount collected gallons easy formula to remember. Rainwater harvesting is collecting the run off from a structure or other impervious surface in order to store it for later use.