When I measured the size of the roof section that drains into the barrel I got 15x27 feet or 405 square feet. If you do the math you get 144x405 square inches of area. If 1.00 inches of rain fell over that many square inches that would amount to 252 gallons. Since last night only 0.37" inches of rain fell that amounts to 0.37 of that amount which is 93 gallons. well that is not 55 gallons so some of the rain escaped the gutters. That can happen because that section of the roof is partially covered by trees and they can adsorb quite a bit of rain as it falls on them, plus my calculations of the number of square feet in the roof could be off.
In general the solution to the equation ((x*144)/231)*.37=55 which comes out to be 238 square feet. So I'm either missing 67 square feet of roof, or the trees absorbed 28 gallons of water or ... THE RAIN BARREL RAN OVER!
Since the little connection at the bottom of the barrel is leaking and the rain barrel was not completely full this morning then a leak could account for this. When just now I did a test it took 1 minute to get 1/3 of a cup which is 20 cups an hour or 1.25 gal/hour and since I first looked at the barrel it was 3 hours ago and it does look like it could be down about 5 gallons and if when it quit raining it had been leaking and running over then that may be where the the 28 gallons of water went. So I'm off to the hardware store again today and I'll purchase another washer for the spigot setup and tighten it down nicely and we will see if we can stop the leak and the next time it rains I'll do more measurements and see how accurate my calculations of the size of the roof are.
Evelyn has a brand new 4x5 garden just across the drive way from the rain barrel. Recently she purchase a soaker hose and has wound it around the garden as well as having it wind through her flower bed next to to the 4x5 garden.
So the 4x5 garden is 20 square feet and the area the rest of the hose wanders through is about the same size or in total probably around 45 square feet.
So she can connect the regular hose pipe to the soaker hose and then to the rain barrel and draw down the barrel about 1/10 or (11 gallons) and that will translate to having her flower bed and garden rained on with 0.37" of rain.
Here is a slide show of some pictures.