The most common diameter of residential gutters in Virginia is 5 inches. A 6-inch K-type foot of gutters holds 2.0 gallons of water. Gutter size is an aspect of rainwater collection that has been studied extensively and can be calculated based on guidelines published in plumbing codes. For example, the Uniform Plumbing Code (UPC) recommends that a gutter system can withstand the runoff of the heaviest 60-minute downpour recorded in last 100 years (e.g., sometimes referred to as storm events).
The International Plumbing Code (IPC) has a similar, but not exact, published size recommendation. Both plumbing code manuals include the size calculations needed to properly size a gutter system. Since water weighs more than 8 pounds per gallon, it represents a significant threat to a home and its inhabitants. The weight of rainwater accumulated on a roof has caused the roofs to collapse.
The gutter system must be able to drain the roof quickly enough not to exceed the structural limits of the roof. Both plumbing codes use the highest amount of rainfall per hour recorded in the last 100 years as a way to ensure that the planned and finally installed gutter system can withstand the largest known rainfall event that has occurred in recent times. To determine system sizing alternatives, know the size of the roof to be drained. In a typical house with two slopes, each side will have gutters and will be dimensioned separately.
Then, calculate how much rain should be drawn from the roof. You can find this number by calling your local building department or looking for the number in Appendix D, Table D1, of the UPC or in Appendix B of the IPC manual. Copies of these manuals are usually available at the local library. For example, for Phoenix* it's 2.2 inches of rain per hour or.
So what size of gutters need to be installed to withstand this incredible volume of rain? The width of the gutters, the slope of the gutters, and the number of downspouts all come into play in determining the correct size of the system. For example, the larger the width of the gutter (i.e., going from a 3-channel to a 5-channel), the smaller the slope required (i.e., e.g.Go from ½ to ¼) to withstand the same amount of rain. Table 11-3-1 of the UPC indicates that a roof that needs to withstand 3450 gallons per hour would require a system designed to the specifications detailed below. TABLE 11-3-1 Uniform Plumbing Code Any of the combinations highlighted above could be installed, depending on the UPC.
The above example assumes that there is only one downspout. Alternatively, several downspouts could be installed and the size of the gutter and the slope requirements would change. To determine these changes, divide the number of precipitation per hour by the number of downspouts. Remember that water is extremely heavy and heavy rainfall can add a lot of weight to the roof surface.
The size of the gutters can and should be calculated and installed in accordance with the requirements of generally accepted building codes. The use of IPC or UPC manuals provides an excellent way to correctly size a gutter system. It is important to note that the CPI and UPC tables differ considerably. The IPC table contains the square footage of the roof area and not the amount of rain that can fall on the roof. Do not confuse the numbers with the same numbers in the table in each manual.
What's the best way to collect rain? Why do I need to collect rainwater? Do I need pumps to collect rainwater? Can I use drip irrigation or rainwater soaker hoses? What size garden can I water? How big are rain barrels? I want more pressure, how should I increase it? In the gutter installation industry, we've done the math. There's a basic formula we use to estimate the amount of rainwater a roof will accumulate based on its size. For every 1000 square feet of roof that receives an inch of rain, 620 gallons of water will flow through the gutters. Consequently, the gutter system must be designed to handle up to 110 gallons per minute or 6600 gallons per hour.
You'll use this GPM calculation to select the appropriate gutter and drain size in step 4: Calculate water handling capacity for gutter and drain options. It depends on many factors, but usually the gutter company determines the slope of the gutters once installed. The water capacity values of a gutter and downspout system are calculated based on the height (flow) of the water that a gutter can hold, the outlet size (hole) of the drain and the number of downspouts used. To avoid this, many homeowners choose to invest in leafless gutters that trap objects at the top of the gutters so that they cannot enter the passage and obstruct the flow of water.
There are several different factors that help determine the size of the gutters each home needs, including the average maximum amount of rainfall in the area, so it can be difficult to know what size of gutter will be the most cost-effective for your specific home. The debris that accumulates on the top is blown away by the wind after drying, which means that these gutters never clog up like gutters do traditional.
