Diverter barrel size: 55 gallons or smaller?

There was a comment on one of the videos describing the diverter: Does the barrel have to be 55 gallons? The answer is no – with several caveats. The volume of water that is diverted depends on the condition and size (surface area) of the roof. The 55 gallon barrel will work for most residential roof surfaces – admittedly it is a bit large for some roof surfaces; however, sometimes it is possible to find used food grade 55 gallon barrels for under 20 dollars; or even free, so cost would be the determining factor. It has been my experience that the condition of the water that comes off of the roof will vary depending on the length of time between rain events, the intensity of the rain event, the temperature, the season of the year, and the surroundings. If you are 100 percent sure of all of the above mentioned situations, then the barrel can be any size you want as long as it is air tight except for a vent to allow for air to escape when water flows in. The amount of water diverted is really best determined by a “guess and check” procedure because all situations will be different. With lots of trees and abundant wildlife here, I prefer to divert about 3 gallons per 100 square feet. One gallon for every 100 square feet is the recommended amount. I have seen water come off of the roof in horrifically foul condition in the summer, and in the winter after a lot of rain, the water is nearly clear. If you are operating a slow sand filter, you want to keep the sediment to a minimum or the filter will plug up quickly. This is why I use a 55 gallon barrel.