How to Install a French Drain in Your Yard (Step-by-Step with Equipment Guide)

By the team at Beehive Rental & Sales — Serving Southern Utah's contractors and homeowners since 1994.

A French drain is one of the simplest and most effective ways to solve yard drainage problems. It is nothing more than a gravel-filled trench with a perforated pipe that collects subsurface water and directs it to a safe discharge point. Despite its simplicity, a properly installed French drain can eliminate standing water, protect your foundation, and rescue waterlogged landscaping --- all for a fraction of what a professional drainage contractor would charge.

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Quick Answer: A French drain requires a trench 18-24 inches deep with a minimum 1% slope toward the discharge point, lined with landscape fabric, filled with drain gravel, and fitted with a 4-inch perforated pipe. A walk-behind trencher from BeeHive Rental & Sales in St. George cuts the trench in hours instead of days of hand digging. Call (435) 628-6663 for trencher availability and project advice.

Key Takeaways

• •A walk-behind trencher cuts installation time by 75% --- a 50-foot French drain that takes a full weekend to hand-dig takes 2-3 hours with a trencher
• •Slope is critical: minimum 1% grade (1 inch of fall per 8 feet of run) or water will sit in the pipe instead of draining; use a laser level to verify before backfilling
• •Always call 811 before trenching --- hitting a buried gas line, water main, or electrical conduit turns a weekend project into a disaster and a liability
• •Southern Utah's clay-heavy desert soil is exactly the condition that creates drainage problems and makes French drains necessary --- our soil drains poorly and caliche layers trap water
• •Browse trenching and drainage equipment at BeeHive --- trenchers, plate compactors, laser levels, and wheelbarrows available for rental

What Is a French Drain and How Does It Work?

A French drain is an underground drainage system consisting of three components working together:

1. •A trench dug along the path where you want to redirect water
2. •Perforated pipe laid in the trench that collects water through small holes along its length
3. •Drain gravel surrounding the pipe that filters soil particles while allowing water to flow freely to the pipe

Water in the surrounding soil enters the gravel, flows through to the perforated pipe, and follows the pipe's slope to a discharge point (daylight outlet, dry well, storm drain, or other approved drainage termination).

The landscape fabric wrapped around the gravel prevents fine soil particles from migrating into the gravel over time, which would eventually clog the system. This fabric is essential for long-term performance.

When You Need a French Drain

• •Standing water in your yard that persists more than 24 hours after rain
• •Water pooling against your foundation despite proper surface grading
• •Soggy, mushy areas in your lawn that never seem to dry out
• •Basement or crawl space moisture coming through walls or floor
• •Downhill water flow from neighbors collecting on your property
• •Retaining wall backfill drainage to prevent hydrostatic pressure buildup

Equipment You'll Need

The right equipment makes French drain installation a one-day project instead of a full weekend of brutal manual labor. Here is what you need and why.

Trencher (Walk-Behind or Ride-On)

The trencher is the single most important piece of rental equipment for this project. A walk-behind trencher cuts a 4-6 inch wide trench to depths of 24-36 inches, producing a clean-walled trench in a fraction of the time it takes to dig by hand.

Walk-behind trencher: Ideal for residential French drains up to 50 feet. You guide the machine along your marked path and it cuts through soil at a steady pace. Handles most Southern Utah soil types, including the rocky conditions common in the St. George area.

Ride-on trencher: For French drains over 50 feet or in very hard soil, a ride-on trencher provides more power and covers ground faster. If your property has extensive drainage needs, the ride-on saves hours.

BeeHive Rental & Sales rents both types and can recommend the right one based on your soil conditions and trench length.

Plate Compactor

After backfilling the trench, a plate compactor settles and compacts the material to prevent future settling that would create a visible depression along your drain path. Without compaction, the trench line will sink over the first few months as the backfill material settles.

Laser Level

Slope is everything in a French drain. A laser level lets you set your trench depth at the starting point and verify consistent slope along the entire run before you lay pipe. Guessing at slope results in flat spots where water pools in the pipe instead of draining.

Wheelbarrow

You will haul a significant amount of gravel into the trench. A sturdy wheelbarrow keeps this process manageable. For a 50-foot French drain, plan on moving approximately 2-3 tons of gravel.

Hand Tools

A shovel, a rake, a tape measure, stakes, and string line round out the essentials. You will also need a utility knife for cutting landscape fabric and a hacksaw for cutting pipe to length.

Materials List

For a standard residential French drain (50-foot run):

• •4-inch perforated drain pipe --- Rigid PVC (preferred for longevity) or corrugated flexible pipe (easier to install but less durable). Buy 10% extra for cuts and fittings.
• •Landscape fabric --- Heavy-duty, non-woven type rated for drainage applications. You need enough to line the entire trench with 6-inch overlap at the top.
• •3/4-inch clean drain gravel --- Washed stone without fines (fine particles). Approximately 1 cubic yard per 10 linear feet of trench. For 50 feet, plan on 5 cubic yards.
• •Pipe fittings --- End caps, couplers, elbows as needed for your layout
• •Drain grate or pop-up emitter --- For the discharge end
• •Backfill material --- Native soil or topsoil for the top 4-6 inches of the trench

Order materials before your rental day. Having gravel, pipe, and fabric on-site before you start the trencher means you can trench, lay pipe, backfill, and return the equipment in a single rental period.

Step-by-Step: Installing Your French Drain

Step 1: Plan Your Route and Slope

Map the path your French drain will follow from the problem area (water collection zone) to the discharge point. Consider:

• •Starting point: The area where water collects or enters your property
• •End point: Where the water will discharge (daylight outlet on a slope, dry well, connection to existing storm drain, or drainage swale)
• •Slope: Minimum 1% grade --- 1 inch of fall per 8 feet of horizontal run. For a 50-foot drain, that means the discharge end must be at least 6 inches lower than the starting end. Steeper is better if your terrain allows it.
• •Path: Follow property contours where possible. Avoid running directly through areas with heavy tree roots or known utility locations.

Step 2: Call 811 for Utility Locates

This step is non-negotiable. Call 811 at least 48 hours before your planned trenching date. A utility locate technician will mark the location of underground gas, electric, water, sewer, and communication lines on your property at no cost.

Hitting a gas line with a trencher is not just expensive --- it is life-threatening. Hitting a water main floods your yard and your neighbor's yard. Hitting a fiber optic line means an angry phone call from the utility company and a repair bill.

In the St. George area, many neighborhoods have shallow irrigation lines, gas lines, and cable TV lines that are easy to hit with a trencher running at 18-24 inches.

Step 3: Mark Your Trench Path

Use stakes and string line to mark the exact trench path. Spray paint the ground along the string to create a visible guide for the trencher operator (you).

Verify your slope calculation by measuring elevation at the start and end points with the laser level. Confirm that you have adequate fall along the entire run.

Step 4: Trench

Fire up the trencher and cut your trench along the marked path.

Trench dimensions:

• •Depth: 18-24 inches (deeper in areas with significant water problems or where you need to route below other utilities)
• •Width: 9-12 inches (the trencher sets this; most walk-behinds cut a 4-6 inch trench, which you will need to widen with a shovel for a standard French drain)

Trenching tips:

• •Keep the trencher moving at a steady pace --- too fast and it bounces; too slow and it bogs
• •Clear the trench spoils to one side as you go, keeping a clean working area
• •Check depth every 10 feet with a tape measure to ensure consistency
• •If you hit a rock or hard layer, let the trencher work through it slowly rather than forcing it

Southern Utah note: St. George area soil often contains caliche layers at 12-18 inches. The trencher will slow down noticeably when it hits caliche. Reduce your forward speed and let the cutting chain do the work. For extremely hard caliche, you may need a more powerful ride-on trencher --- discuss your soil conditions with the BeeHive Rental team before your rental.

Step 5: Verify Slope

Before any pipe or gravel goes in the trench, verify your slope.

1. •Set up the laser level at one end of the trench
2. •Place the measuring rod at the opposite end
3. •Check that the trench bottom drops at least 1 inch per 8 feet along the entire run
4. •If you find flat spots or reverse grades, deepen those sections with a shovel

This is the step most people skip, and it is the reason most French drains fail. A flat spot in a French drain becomes a standing water reservoir that breeds mosquitoes, grows algae, and eventually clogs. Verify your slope before proceeding.

Step 6: Line the Trench with Landscape Fabric

Roll landscape fabric along the bottom and up both sides of the trench, leaving enough excess on each side to fold over and overlap at the top later. The fabric should cover the entire trench interior with no gaps.

The fabric serves as a filter --- it allows water through while preventing fine soil particles from migrating into your gravel and pipe, which would clog the system over time.

Step 7: Add Base Gravel and Place Pipe

1. •Shovel 2-3 inches of clean drain gravel into the fabric-lined trench bottom
2. •Lay the perforated pipe on top of the gravel base with the perforations (holes) facing down
3. •Connect pipe sections with appropriate couplers
4. •Ensure the pipe follows the slope of the trench --- it should not sag or bow between supports

Holes facing down is correct. This seems counterintuitive, but the pipe collects water that rises up from the gravel beneath it. The gravel below the pipe acts as a reservoir that feeds into the pipe from below.

Step 8: Backfill with Gravel

Fill around and over the pipe with clean drain gravel to within 4-6 inches of the ground surface. The gravel should completely surround the pipe on all sides with at least 2-3 inches of coverage above the pipe.

Use the wheelbarrow to transport gravel from your stockpile to the trench. For a 50-foot drain, this is the most physically demanding part of the project --- 5 cubic yards of gravel weighs approximately 7-8 tons.

Step 9: Wrap the Fabric and Backfill

Fold the excess landscape fabric over the top of the gravel, overlapping the edges by at least 6 inches. This creates a complete fabric envelope around the gravel that prevents soil infiltration from above.

Fill the remaining 4-6 inches with native soil or topsoil. Mound the backfill slightly above the surrounding grade to account for settling.

Step 10: Compact and Finish

Run the plate compactor along the backfilled trench to settle the material. The surface will drop noticeably after compaction --- add additional soil as needed to bring it level with the surrounding grade.

Seed or sod the trench path to prevent erosion. In Southern Utah, the trench line will be invisible within one growing season if you establish vegetation promptly.

Critical Slope Calculation

Getting the slope right is the single most important technical aspect of French drain installation. Here is the math:

Minimum slope: 1% grade = 1 inch of fall per 8 feet of run

Preferred slope: 2% grade = 1 inch of fall per 4 feet of run (this moves water faster and is more forgiving of minor installation errors)

If your terrain does not provide enough natural fall over the drain length, you will need to dig the starting end deeper to create adequate slope. This is common in flat yards --- the drain starts deep and exits at or near grade level at the discharge point.

Southern Utah Drainage Considerations

Desert Clay Soil

Despite the sandy appearance of some Southern Utah soil, much of the St. George area has significant clay content mixed with sand and rock. This clay component is exactly what causes drainage problems --- clay particles pack tightly, creating an impermeable layer that traps water near the surface. French drains cut through this layer and provide an escape route for trapped water.

Caliche Layers

Caliche --- a hard, calcium carbonate layer common in desert soils --- acts as a natural barrier that prevents water from percolating downward. Many St. George yard drainage problems exist specifically because water cannot penetrate the caliche layer and has nowhere to go. A French drain provides the path that caliche blocks naturally.

Monsoon Season Flooding

Southern Utah's monsoon season (July through September) delivers intense, short-duration storms that dump large volumes of water in minutes. A properly sized French drain handles normal rainfall events, but monsoon deluges can overwhelm any residential drainage system temporarily. Size your drain conservatively and ensure the discharge point can handle high-volume flow.

New Construction Drainage

Many newer subdivisions in Washington County have drainage problems caused by heavy equipment compacting the soil during construction. This compaction creates an artificial impermeable layer similar to caliche. French drains are one of the most effective solutions for post-construction drainage issues. BeeHive Rental & Sales sees a steady stream of new-subdivision homeowners renting trenchers for exactly this reason.

Cost Comparison: DIY vs. Hiring Out

The labor component is where DIY delivers massive savings. Materials cost the same whether you install or a professional installs. The difference is labor --- and a trencher rental eliminates the hardest part of that labor. For a 50-foot French drain, you save $1,500-$5,000 by renting a trencher and doing the work yourself.

FAQ

How deep should a French drain be?

A residential French drain should be 18-24 inches deep for most yard drainage applications. If the drain is intended to protect a basement or crawl space, it should be deeper --- typically to the level of the foundation footing. The key constraint is maintaining minimum 1% slope from the collection point to the discharge point while staying deep enough to collect subsurface water.

How long does a French drain last?

A properly installed French drain with landscape fabric, clean gravel, and quality pipe will last 20-30 years or more. The most common failure mode is fabric or gravel clogging from soil infiltration, which is prevented by using proper non-woven landscape fabric and maintaining the fabric envelope integrity during installation. Avoid using perforated pipe with a fabric sock (pipe wrapped in fabric) as the sole filter --- the sock clogs faster than fabric-wrapped bulk gravel.

Can I install a French drain without a trencher?

You can dig a French drain trench by hand with a shovel and a trenching spade. For a 50-foot drain at 18 inches deep, expect 8-16 hours of digging, depending on soil conditions. In Southern Utah's rocky, compacted soil, hand-digging is extremely difficult. A trencher rental from BeeHive Rental & Sales cuts the trenching time to 2-3 hours and costs far less than the back pain from two days of manual digging.

Where should a French drain discharge?

The discharge point must be somewhere water can exit safely without causing problems for you or your neighbors. Common options include: a daylight outlet on a slope where water flows into a natural drainage area, a dry well (underground chamber that slowly releases water into surrounding soil), connection to an existing storm drain (with city approval), or a drainage swale that directs water to the street. In St. George, check with the city about approved discharge locations, especially if your property borders a wash or flood zone.

Do I need a permit for a French drain in St. George?

Standard residential French drains typically do not require a permit in St. George. However, if your drain discharges into a public storm drain, crosses property lines, or involves significant excavation near a wash or flood zone, contact the City of St. George at (435) 627-4830 to confirm. You must call 811 for utility locates before trenching regardless of permit requirements.

Ready to fix your drainage problem? BeeHive Rental & Sales in St. George has trenchers, plate compactors, laser levels, and all the equipment you need for a French drain installation. The team understands Southern Utah's unique soil conditions and can help you choose the right trencher for your specific project. Call (435) 628-6663 for availability, or browse the equipment inventory to start planning.