A French drain collects subsurface water through a permeable trench and carries it to an appropriate outlet. Start by identifying the water source and confirming where it can legally discharge. A drain is not an automatic cure for every wet yard or basement.
1. Diagnose the Water Problem
Inspect gutters, downspouts, grading, and possible plumbing leaks before digging. Surface ponding may need a surface inlet or grading work; basement leaks can require a foundation specialist. Identify whether the proposed drain addresses the actual cause.
2. Confirm the Route and Outlet
Plan the collection area, pipe route, and accessible outlet together. Check local stormwater and permit requirements with the responsible authority. Do not assume permission to discharge onto a neighboring lot, into a waterway, or into a sewer. If there is no suitable gravity outlet, obtain a site-specific design rather than simply digging deeper.
3. Locate Buried Utilities
In the United States, contact 811 before digging and follow your state’s notice, marking, and excavation requirements. Confirm all required responses before starting. Privately owned lines, such as irrigation, power to a shed, or a pool supply, may need a separate locator. Markings do not establish a safe digging depth.
4. Specify the System
Select pipe, fittings, drainage aggregate, and filtration materials for the site and the chosen manufacturer’s instructions. There is no universal trench size or building setback suitable for every installation. Work near foundations, retaining walls, major roots, or deep excavations requires qualified help.
Use purpose-made drainage pipe instead of improvising perforations in an ordinary pipe. Plan cleanouts or other maintenance access where the design calls for them. A grated surface inlet is an optional design component, not a requirement of every French drain.
5. Establish a Continuous Fall
Measure elevations along the planned route and check the specified grade while excavating. A 1% grade means 1.2 inches of fall over 10 feet; one inch over 10 feet is about 0.83%. These figures explain the calculation, not a universal minimum: use the grade required by your system and site design.
6. Prepare the Trench and Bedding
Follow the designed dimensions and use appropriate equipment and excavation practices. Do not undermine structures or enter an unsupported excavation. Place the specified permeable filtration material and bedding; ordinary weed-control fabric is not automatically suitable. Filtration reduces soil intrusion but does not guarantee protection from roots or future clogging.
7. Install and Check the Pipe
Connect the collection pipe and outlet components as specified. Follow the particular pipe’s instructions for slot or hole orientation rather than applying one rule to all products. Check elevations, secure joints, and test the accessible system before covering it. Correct low spots or a blocked outlet now.
8. Finish and Record the Installation
Complete the aggregate, filtration, and surface finish according to the design. Keep cleanouts and any inlet accessible. Photograph the route before covering it and keep product information and an outlet location record for future maintenance.
Maintain the Drain
Inspect accessible inlets and the outlet after heavy rain, remove visible debris, and watch for renewed ponding. If flow declines, investigate the blockage rather than assuming the whole system must be replaced. A drainage professional can assess buried obstructions and repairs. A simple flow test does not prove that the system is sized for a major storm.
Consult NDS’s installation guidance for system planning and your product’s detailed instructions, and OHIO811’s explanation of private utilities for why additional locating may be needed. Local requirements and the specific installation design govern the work.
