I usually dig a trench about 12 to 14 inches deep for downspout drain lines. If the lot is fairly flat, the pipes will get deeper the farther they extend, as you should create 1/8 inch of fall for every foot the pipes run.
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Frequently Asked Questions
What's the minimum depth for a drain pipe?
The minimum depth is typically 18 to 24 inches. This depth helps capture most of the water that's an issue. If your goal is to protect your foundation or keep water from getting into the basement, you want your pipe installed deep enough to achieve that goal.
How big should an underground drainage ditch be?
A typical drainage ditch is 12 to 18 inches deep and 6 inches wide.
What do you need to know about underground drainage pipes?
Underground drainage pipes are a simple way to drain areas that are prone to remaining wet long after any significant rainfall. Drainage pipes are typically placed around the perimeter of foundation to collect excess water, which is then connected to one or more drainage pipes that lead away from the home or lawn on a downward slope.