Downspout Selection and Filter Placement
A good guideline is to be able to fill up half of your pillow from one inch of rain.
Evaluate the number, location and efficiency of your downspouts
1. Is there access to the pillow from downspout?
2. Would a filter be acceptable at this location?
3. Would gravity feed the pillow from the filter (bottom valve of the filter must be above height of full pillow)?
4. Over flow (can it be directed into a present drainage system or redirected into the garden and away from the house)
5. Calculate the gallons of water directed to this downspout from one inch of rain
Horizontal length x width of roof area (estimate if multiple downspouts)
The multiply the roof area by .625 to determine the gallons per inch of rain that will be directed to this downspout
Continue with this evaluation for each of the downspouts to determine which are the best to use to maximize your collection volume.