Calculating Rainwater

The Collection Surface

Sketches of three different roof footprints
Photo credit: ARCSA

The roof, or the Collection Surface is where rainwater stops becoming rain, and becomes stormwater. This is where jurisdictions are struggling to control this stormwater runoff, and actually requiring on-site retention on all commercial development. As private property owners, we can safely and legally collect and store rainwater, or stormwater, but in order to determine how much we can potentially collect, we must first calculate the area in which it falls. We call this, the Collection Surface.

The example shows what a typical roof footprint might look like. The actual roof area is not important, or even the complexity of the design, but the actual roof footprint, or Collection Surface.



The Storage Facility

Photo of a 500 gallon cistern prior to being buried for a private rainwater harvesting system.
A 500 gallon cistern.

The rain barrels, cisterns, and tanks, or the Storage Facility, is where our rainwater is stored. Selecting the right system is dependent on many factors, and there is a multitude of designs to choose from. A few factors to consider is the size of your property and your location constraints. Your budget is important, and also the area where you live that will determine the amount of actual rainwater that can be, or needs to be, collected. Please read the article titled, Rainwater Collecting Systems. This may provide some alternatives to assist in determining a system that is right for you. Please do not hesitate to contact us for a free initial consultation.

The calculator, below, will provide a basic estimate of the amount of rainwater that can be collected, based on a given area. There are other factors that play a role in determining this amount, but this is a good starting point.



Congratulations, you did it!

This is roughly the amount of Rainwater that you will be collecting (annually) from this particular portion of your roof. Feel free to give us a call at (520) 477-1447 if you have any questions, and need assistance on taking the next step to collecting Rainwater.