A sump pump drain line that lies on top of the lawn can be a problem, because it must be moved regularly for lawn-mowing and presents a trip-and-fall hazard in the yard. Those headaches are avoided with a buried sump pump drain line. An underground sump pump drain line can be prone to freezing, however, if it isn't deep enough, so check with your local municipal office for the depth of the frost line in your area and install the sump pump line below the frost line.
Dig a trench for the sump pump drain line that is at least 2 feet wide and the depth of the frost line in your area, plus an additional 2 feet. For example, if the frost line in your area is 12 inches, dig the trench 3 feet deep. Remove the sod in pieces and place to the side so it can be re-used to cover the trench.
Create the proper slope to drain the water away from the house by, first, tying a string to a stake at the beginning of the trench and attach it to a stake at the end of the trench. Level the string with a line level. Place the line level on the string and adjust the string on each stake until it is level.
Measure the string with a tape measure. For each 8 feet of string, the slope should be 1 inch. Divide the total feet of the trench by 8 to get the needed slope. Move the string attached to the stake at the end of the trench down the necessary distance for the slope. For example, if the string is 16 feet long, the necessary slope for proper drainage is 2 inches. Push the string on the stake at the end of the trench down 2 inches.
The bottom of the trench must be the same distance from the string the entire length of the trench. Start from the beginning of the trench, where the water will be leaving the sump pump. Measure the gap between the string and the bottom of the trench. Follow the trench and dig or fill as needed to maintain the same distance from the bottom of the trench for the entire length of the trench.
Place the rigid hose in the trench so the top end is as close to the sump pump as possible.
Attach the sump pump drain line to the sump pump. Attach the more flexible sump pump drain line hose to the rigid hose in the trench with a wire band and tighten the screw with a screwdriver.
Place a screen over the opening to prevent animals from making nests in the drain line.
Replace soil, and then sod, back in the trench. Gently press the sod down by walking on it and water thoroughly to encourage growth.