Q: Here is a link to a web site where I found a barrel/cistern for water retention and re-use. My question is, are these viable options for detaining water? Do these things work?

A: All depends on how much water you’re trying to detain….and how many barrels/cisterns you can afford.

In a one inch rain, twelve square feet of roof area collects a cubic foot of water. A cubic foot of water equals 7.5 gallons.

A rough estimate is that a thousand square feet of roof area would collect 625 gallons of water….more than 12 fifty-gallon barrels.

I’ll let you do the math and make the decision.