Next week I will be going to place the order for the remainder of rainwater tanks I need to complete the system. I will order 2 more 3000 gallon tanks and seven 2500 gallon tanks that will fit under my big deck. It will give me a total storage capacity of 26,500 gallons. My system is such that I can gather 1400 gallons per inch of rain off of my garage roof and 3000 gallons per inch off of my house roof. Sounds like a LOT of storage, but when it rains here in Texas it usually rains a LOT at one time and to be effective you need to have the storage capacity to catch the rainwater. Its not unusual to get 3-4 inches at one time. That means I'd need to have available storage for 13,200 - 17,600 gallons to be truely effective and prevent wasting water. Even a 3/4 inch rainstorm means that I have to have 3,300 gallons of free storage. We average 32 inches of rain per year so in an average year I have the possibility of catching 142,000 gallons or an average of about 12,000 gallons per month. The conundrum is that in a normal rainfall year I need to only do minor irrigation of fruit trees and gardens, and don't need the storage. Assuming a half rainfall year at 6,000 gallons per month I can't do much irrigation even though that is when I need the water the most, and even the storage I have won't help much, but would keep the trees and gardens alive. What I really need is less tanks and a 50 by 50 by 10 ft deep pond to catch the overflow from the tanks. 25,000 cubic feet of water would be about 200,000 gallons, about 12 times the storage I will have.