With 9 x 10,000 gallon welded-steel tanks, we have a total of 90,000 gallons of storage capacity. 3-tanks will hold up to 30,000 gallons of rainwater from the roof, and 4-tanks will hold up to 40,000 gallons of stormwater collected from area drains around the grounds of the property. Rainwater from the roof is the primary source for all indoor water use, and stormwater from the site is dedicated to irrigation and fire suppression. One of those four stormwater tanks is dedicated to fire suppression (we are required by the county to have one 10,000 gallon fire suppression tank.)
The rain over the last few days brought us around 2500 gallons of rainwater off of the roof. We estimate that water will provide about 20-days of indoor water use. If we keep getting rains like this in the next month, we should not have to fill the rainwater tanks with any municipal water prior to move-in. Keeping our fingers crossed!