The slope of a horizontal drainage pipe shall be not less than that indicated in Table 704.1 except that where the drainage piping is upstream of a grease interceptor, the slope of the piping shall be not less than 1/4 inch per foot (2-percent slope).
A 2% slope means that a surface (such as a road or a train track) change in elevation by 2 units over a run of 100 units. This means that a 2% slope is present when the rise changes by 2 meters (or feet) over a run of 100 metres (or feet).
So: How do I get 2%?
1/4" drop per foot. About 1' over 50' or 2' over 100'.
Driveways should be sloped with a minimum 2% slope—anything lower will cause precipitation and runoff to collect. A 2% slope is the equivalent of a 2-foot rise over 100 feet.
2% is 1 in 50, so a 2% slope is roughly 1/4″ rise per foot.
The pitch should be a minimum of 1 inch for every 10 feet, but 1 1/2 inches is recommended. If this is not done, it will almost definitely result in a water problem.
For example, suppose you go up two feet as you go forward 100 feet. That's a 2% grade. Suppose you climb eight feet as you go forward 100 feet. That's an 8% gradient.
Using a minimum slope of 2% will encourage a good flow when directing water to a rain garden. For a 2% slope your pipe height will lower ~¼ inch for every foot of length. You can also approximate this by multiplying the pipe length in inches by . 02.
A 2% grade means an elevation change of 2 feet for every 100 feet of horizontal distance. For a horizontal distance of 75 feet, the elevation increases by 1.5 feet. This calculation illustrates the concept of slope as rise over run.
A 2% slope is the same as a 2% grade. This means that the elevation changes by 2 ft for each 100 linear ft. Since a mile is 5280 ft, a 2% slope means an increase or decrease of 105.6 ft.
You can enter 4:12 for a four in twelve roof pitch or 2:100 for a two percent slope.
The Portland Cement Association (PCA) publication Building Quality Concrete Parking Areas recommends sloping the pavement 1 percent to drainage. The American Concrete Institute's (ACI) Guide for Concrete Floor and Slab Construction recommends a slope of about 2 percent (1 inch in 4 feet) to provide positive drainage.
To promote proper drainage, your yard and landscaping should have a slope of at least 3% directed away from your home's foundation, and generally between 3-10%, though grades of anywhere from 3% to 25% may be acceptable.
The slope of a horizontal drainage pipe shall be not less than that indicated in Table 704.1 except that where the drainage piping is upstream of a grease interceptor, the slope of the piping shall be not less than 1/4 inch per foot (2-percent slope). For SI: 1 inch = 25.4 mm, 1 inch per foot = 83.33 mm/m.
Pavement is typically laid at a cross-slope of 2%, or ¼” of fall per horizontal foot of road width measured from the centerline toward the ditch. On unpaved surfaces, the recommended cross-slope is between 4% and 6%, or ½” to ¾” of fall per horizontal foot of width from the centerline toward the ditch.
The slope of a line is a measure of its steepness. Mathematically, slope is calculated as "rise over run" (change in y divided by change in x).
A 1% slope is 1 in 100. If we now devide both sides by 100 we get 0.12 in 12. This then gives us a rise of 0.12 inches per foot.
Channel drains are long, narrow drains installed at the edge of the driveway or in the middle to capture surface water and direct it away. Available in various weight load classes, they're highly effective at preventing surface flooding.
Pitch on a house drain
The general rule is 1/4″ of pitch per foot of run.
A well-constructed concrete surface should have a slight slope to allow water to flow away from the surface. The recommended slope is typically 1/8 to 1/4 inch per foot, depending on the size of the area.