Rain Harvesting Calculator
The rain harvesting calculator calculates the amount of rainwater harvested from a given square footage of rain catchment area plus the inches of rainfall.
Building a Rain Harvesting System
I began planning the design of my rain-catchment system shortly after I bought a piece of rural property that had no viable access to the public water system.
Digging a well was an option, but I heard too many stories about people who dug wells, then later had to deepen them as more people dug wells around them and lowered the water table.
Since I wasn't planning to live on the property (yet), I decided that a rain catchment system was the ideal solution. A rain catchment system would be easy for me to construct and - with the right size tank - could store the water I needed for mixing concrete and taking showers.
On my property, I built an RV shelter that serves as a docking station for my travel trailer on weekends. It has a 34' x 17' sheet metal shed-style roof perfect for a rain catchment system. I installed a gutter along the length of the lower end of the roof and a 450-gallon tank to store the rainwater.
Using the Rain Harvesting Calculator
I used the Rain Harvesting Calculator to determine how much rainwater I could capture with 1 inch of rainwater on my 34' x 17' roof. The result was 360.3 gallons! It doesn't seem possible, but it adds up quickly.
Building a Rain Harvesting System at Your Home
The easiest way to harvest rainwater at your home is to add a gutter system and store the rainwater that lands on your roof in a rain barrel. If you already have gutters installed, you are halfway there.
Cistern size should be adequate to supply your water needs during extended periods of low rainfall.
Place the water reservoir on blocks high enough to take advantage of gravity when watering your plants.
You can build a taller platform out of wood or steel to support your rain tank, but you need to ensure it is strong enough to support the tank when it is full of water. 360.3 gallons @ 8.34 pounds per gallon weighs just over 3,000 pounds!
The slope or pitch of the roof does not play a part in the catchment area calculation. The calculation comes from the horizontal measurement between the roof's upper and lower vertical points.
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What next?
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