The depth of the trench should be at least 18 inches to allow room for: A gravel base, Drain pipe, Rock gravel, Topsoil. It helps to think about the slope of the trench, which should be at least 1 inch per 10 feet run. This ensures the outlet will be at least 10 inches deeper at the end of a 100-feet run.
Dig a Trench
The trench should be about 18 inches deep and 9 to 12 inches wide. least 1 percent, so the force of gravity will work for you. This means that the drain should slope down a total of at least one inch for every 10 feet of pipe.
Adding drainage to a backyard does not have to be a complicated project. One drainage solution might be installing dry-wells in the areas that tend to get the most water. A dry well is simply a deep hole filled with gravel to allow water to reach a more permeable soil.
RPE (Reinforced Polyethylene)
RPE is often recommended as the preferred material for lining drainage ditches. Its high strength-to-weight ratio, combined with its flexibility and ease of installation, makes it a cost-effective and reliable choice.
Unless there are specific flow velocity requirements (ex. airport runways), neutral channels will not significantly affect drainage. Even a system comprised of all neutral channels, on a level grade, will drain to the outlet. However, flow through a sloped system does help flush debris, and keep the channels clean.
Residential sewer line pipe depths range from as shallow as 18 to 30 inches in depth or 5 to 6 feet deep. However, in colder climates where freezes occur, you often see sewer line depths ranging from 4 to 8 feet deep. This ensures the pipes are below the freeze line.
Backfill the Trench With Concrete
To ensure the drain channel is secure, you want to do this process in two steps: first, floating the channel 1/16-inch below the first layer of concrete. Then, once it has set, backfill the rest of the trench with at least 4-inches of concrete on both sides.
The average cost to dig a trench is $950 per 100 linear feet, but prices can range from $400 to $1,200 depending on the purpose of your project, such as a drainage system or laying gas pipes. You should budget anywhere from $5 to $12 per linear foot to dig a trench or $13 to $40 per linear foot for major projects.
Pipe for conveying liquids susceptible to freezing should be buried no less than 12" below the maximum frost level. Permanent lines subject to heavy traffic should have a minimum cover of 24". For light traffic, 12" to 18" is normally sufficient for small diameter pipe (typically < 3" diameter).
Aside from what we've listed here, the difference between a French drain and a trench drain is that a French drain is used for water that is underground while a trench drain diverts excess water from a surface.
Use a shovel or a hoe to dig out an area large enough to accommodate an average-sized drain pipe. We recommend digging it about one foot wide and 18 inches deep. The wider the trench, the easier it is to collect water and the lower the chance of clogging.
When using hand tools, begin by loosening the soil with a pick mattock or grub hoe and remove rocks and other hard obstructions. Dig with a trenching shovel, making sure to shape the walls of the trench. Use the grub hoe or rake to remove the loose soil from the trench.
All drainage pipes should be placed on the gravel bed in the trench. PVC drainpipe, if used, should be placed in the trench with the holes facing down.
Depth and Width Considerations
The trench should be at least 12 inches deep and wide enough to accommodate your pipe. This depth allows for sufficient soil coverage and protection from surface activities, ensuring that the pipe remains undisturbed and functions effectively.
Once you start digging your drain depth will need to be anywhere from eight inches to two feet, depending on your needs and available options.
As a general rule, any trench drain that is installed in doors should be attached to some form of trap.
If you've ever wondered what the minimum slope for water drainage is, it is generally accepted that 1/4″ per foot of pipe run is the minimum for proper pitch on a sewer line. Larger lines such as 8″ pipe actually require less pitch due to the larger circumference of the pipe.
Regular trench drains run from around 4 1/2” deep to upwards of 17” deep. Shallow trench drains run from 2 1/4” to 3 1/2' deep. Because of the height restrictions, shallow trench drains do not come in pre-sloped.
Rocks for Drainage
Its purpose is to carry water from where it's not wanted to where it can do less harm. A rock drainage ditch refers to when one uses rocks in a drainage ditch to assist with the water flow, to prevent erosion alongside roads and driveways, and to help prevent erosion on lots with steep slopes.
Things You Should Know
Dig a trench and line it with landscape fabric. Add gravel to the bottom of the trench before laying down your drain pipe. Cover the drain pipe in gravel, then fill in the rest of the trench with the displaced dirt you dug up before.
Ideally a series of check dams should be installed along the length of the ditch. At minimum, a check dam at the downstream end of the ditch will prevent sediment from leaving the ditch.