What is the depth of the trench that needs to be excavated if the incline of the sewer line is 1/8 inch per foot?

To understand why a depth of 2 feet 2.5 inches below the finish grade stake is correct for the trench excavation given an incline of 1/8 inch per foot, it's essential to consider how the slope of the sewer line translates into depth over a distance.

The incline of 1/8 inch per foot means that for every foot of horizontal distance, the sewer line drops 1/8 inch vertically. To find the necessary depth at a set distance, this incline needs to be multiplied by the total horizontal run of the sewer line.

For example, if the length of the sewer line being installed is 25 feet, you would calculate the total drop as follows:

1/8 inch per foot x 25 feet = 25/8 inches = 3.125 inches.

To convert 3.125 inches to feet, it’s essential to realize that 12 inches equals 1 foot; thus, 3.125 inches is equivalent to approximately 0.26 feet.

Now, when combining the mandatory depth of the sewer line with the need to ensure that the line is appropriately buried below the finish grade stake, the final depth is established.

A depth of 2 feet 2.5 inches below the