Gutter ProTech

Rain Flow Rate

Gutter ProTech® rain gutter protection panels can capture in excess of 22 inches of rain per hour on an average roof. This rate is almost double the record rainfall recorded anywhere in the USA. The Gutter ProTech® panel on the model used for demonstrations at shows captures and delivers into the gutter 300 gallons per hour over 18 inches. This means that this Gutter ProTech® panel is capturing water and delivering it into the rain gutter at a rate of 16.7 gallons per hour, per inch of gutter. If the width (or "d" in the equation below) of the house is 180 inches, rain would have to fall at the rate of 21.4 inches in an hour to produce this flow.

To convert between inches of rain per hour and gallons per inch per hour, we need to know the horizontal distance from the eaves to the crown of the roof. On a typical house this will be half the width of the house; labeled d in the diagram. For the calculations below d is measured in inches.

If x inches of rain fall, xd cubic inches will flow across an inch of gutter, on average.D
There are 231 cubic inches in one gallon. So if x inches of rain fall per hour there will be a flow of xd/231 gallons per hour across an inch of gutter. For example: If d is 15'=180", and the rain fall is 2" in an hour, then the flow over each inch of gutter will be 180 * 2/231=1.5 gallons per hour. Note that the demonstration model captures 16.7 gallons per
hour per inch of gutter; far more than the record rainfall ever recorded in the USA.