In 2026, a professionally installed French drain typically costs between $20 and $50 per linear foot, with most residential jobs landing in the $25–$35 range. That means a 50-foot run to daylight — enough to handle a typical yard drainage problem — will run you somewhere around $1,250 to $1,750 installed. The wide spread comes down to excavation difficulty, how deep you need to go, whether you're tying into a dry well or just running to daylight, and local labor rates.
DIY brings the cost down substantially — you're looking at roughly $8 to $15 per linear foot in materials if you rent a trench digger and do the labor yourself. The catch is that digging a straight, sloped trench through roots, clay, or rocks is genuinely hard work, and getting the slope wrong means the drain doesn't work. This guide walks through what goes into a French drain, how to size the materials, and where the money actually goes.
2026 French drain cost per linear foot
| Install type | Cost per linear foot | Notes |
|---|---|---|
| DIY (materials only) | $8–$15 | Perforated pipe, gravel, fabric. You do the digging and backfill. |
| Contractor (shallow, easy access) | $20–$30 | 12–18″ deep, open yard, machine excavation. |
| Contractor (deep or difficult) | $30–$50 | 24″+ depth, tight access, roots, rocky soil, or tie-in to dry well. |
| Exterior foundation drain | $50–$100+ | Exterior footing drains around a house. Deep excavation, waterproofing tie-in. |
These are installed prices for a basic trench drain that runs to daylight (an exit point where water can flow out). If you need a dry well at the end because there's nowhere for the water to go, add another $800 to $2,000 for the dry well itself — more if it's deep or you're in heavy clay. The Dry Well Calculator sizes the pit based on your drainage load.
What actually goes into a French drain
A French drain is simpler than most people think — it's a sloped trench filled with gravel and a perforated pipe that collects groundwater and carries it somewhere useful (downhill to daylight, into a dry well, or to a storm drain if local code allows). The parts list is short: pipe, gravel, landscape fabric, and a trench. The work is in the digging and getting the slope right.
Here's the anatomy from top to bottom:
- Trench: Typically 12–18 inches deep and 6–12 inches wide. Deeper if you're intercepting a high water table or working around a foundation. Sloped at 1–2% grade — that's about ⅛ to ¼ inch of drop per foot of run. Any less and water sits; any more is fine but means digging deeper at the outlet.
- Landscape fabric: Lines the trench to keep soil from clogging the gravel. You'll lay it in the bottom and up the sides, then wrap it over the top after the pipe and gravel go in.
- Gravel: Crushed stone, usually #57 or similar clean stone (¾-inch), fills the trench around the pipe. This is the actual drainage reservoir — water flows through the voids between stones and into the pipe perforations.
- Perforated pipe: 4-inch corrugated or Schedule 40 PVC with holes or slots. Laid perforations down (yes, down — the water enters from below as the trench fills). Solid pipe at the outlet so water doesn't leak before it exits.
- Backfill: Gravel to within a few inches of grade, then topsoil or mulch on top to hide it.
The slope is non-negotiable. A level trench turns into a gravel-lined ditch that holds water instead of moving it. Use a string line and a level, or shoot it with a laser level if you're doing a long run. The French Drain Calculator helps you size the trench and calculate gravel volume based on length, width, and depth.
Trench dimensions and depth
Most residential French drains are dug 12 to 18 inches deep and 6 to 12 inches wide. That's deep enough to intercept shallow groundwater and wide enough to hold sufficient gravel for decent flow. If you're dealing with a high water table, a soggy lawn, or trying to protect a foundation, you may need to go deeper — 24 inches or more. Deeper trenches cost more to dig and need more gravel, but they're sometimes the only solution.
| Application | Depth | Width | Gravel per linear foot |
|---|---|---|---|
| Shallow yard drainage | 12" | 8" | ~0.025 cu yd (~65 lb) |
| Standard curtain drain | 18" | 10" | ~0.046 cu yd (~120 lb) |
| Deep intercept or foundation | 24" | 12" | ~0.074 cu yd (~200 lb) |
The gravel quantities assume crushed stone at roughly 2,600 lb per cubic yard. For a 50-foot run at standard depth (18″ × 10″), you're looking at about 2.3 cubic yards of gravel, or around 3 tons. Use the Gravel Calculator to convert trench volume into tons or yards, and always order a bit extra — trenches are never perfectly uniform.
Materials breakdown: what you'll actually buy
Let's price the materials for a 50-foot French drain at standard depth (18 inches deep, 10 inches wide), the most common residential size. This is a DIY materials list — if you hire it out, the contractor buys this and marks it up as part of the installed price.
| Material | Quantity | Unit cost | Total |
|---|---|---|---|
| Perforated 4″ corrugated pipe | 50 ft | ~$1.20/ft | $60 |
| Crushed stone #57 (¾″) | 2.5 cu yd | ~$40/yd delivered | $100 |
| Landscape fabric (4 ft wide) | ~70 ft | ~$0.30/ft | $21 |
| End cap & fittings | Misc | — | $15 |
| Topsoil backfill (optional) | ~0.5 cu yd | ~$35/yd | $18 |
| Materials total | ~$214 | ||
| Trencher rental (1 day) | 1 day | ~$150–$250 | $200 |
| DIY total | ~$414 |
That works out to about $8.30 per linear foot in materials, or closer to $8.30 + $4 = $12.30 per foot if you include the trencher rental. Compare that to a contractor install at $25–$35 per foot and you're saving roughly $600 to $1,100 on a 50-foot run by doing it yourself. The trade is a long day of trench work — digging, leveling, laying fabric and pipe, backfilling gravel, and cleaning up.
French drain essentials
- Slope the trench 1–2% (⅛ to ¼ inch per foot) for reliable flow.
- Lay perforated pipe with holes facing down — water enters from below.
- Wrap the gravel in landscape fabric to keep silt out; it clogs fast without it.
- Use clean crushed stone (#57 or similar), not round river rock — angular stone drains better.
- Outlet to daylight if possible; if not, size a dry well with the dry well calculator.
Where the cost goes: DIY versus contractor
The material cost is the same whether you do it yourself or hire it out — pipe, gravel, and fabric are fixed. The contractor markup on materials is modest, maybe 10–20%. The real money is in labor, and specifically in excavation. Digging a straight, sloped trench through roots and clay is hard, slow work by hand, and even with a trencher it takes experience to get it right.
| Approach | Materials | Labor / rentals | Total | Your time |
|---|---|---|---|---|
| DIY | $214 | $200 (trencher) | ~$414 | 1–2 days |
| Contractor | $250 | $1,000–$1,500 | $1,250–$1,750 | Half a day |
If you're comfortable operating a trencher, have decent soil, and the run isn't obstructed by roots or rocks, DIY is genuinely doable and saves you a thousand bucks. If your soil is heavy clay, the trench crosses under driveways or sidewalks, or you're not confident getting the slope right, hiring it out is usually worth it — a French drain that doesn't drain is worse than no drain at all.
When you need a dry well tie-in
A French drain works best when it can outlet to daylight — meaning the end of the pipe spills out onto a slope, into a storm drain, or into a street gutter where water can flow away. But plenty of yards don't have a good outlet. Maybe the lot is flat, or the low spot is in the middle of the yard with no downhill path. That's when you tie the French drain into a dry well.
A dry well is a buried pit — usually 3 to 5 feet deep and 2 to 4 feet in diameter — filled with gravel or a perforated drum. Water flows from the French drain into the well and percolates into the surrounding soil. Dry wells work great in sandy or loamy soil; they struggle in heavy clay unless you make them large. The Dry Well Calculator sizes the pit based on your expected drainage volume and soil type.
Adding a dry well to a French drain project typically adds $800 to $2,000 to the total cost — $400 to $700 in materials (the pit liner or gravel, fabric, and excavation) and the rest in labor for digging a deep hole. DIY is possible but it's hard work; a 4-foot-deep, 3-foot-diameter hole is roughly 28 cubic feet of soil you're moving with a shovel.
Slope requirements and why they matter
A French drain relies entirely on gravity. Water flows downhill through the gravel and into the pipe, then downhill again through the pipe to the outlet. If the trench is level or — worse — slopes the wrong way, water sits. You'll have a permanently soggy gravel trench instead of a drain.
The minimum slope is 1%, which is about ⅛ inch of drop per foot. Most installers aim for 1.5–2%, or about ¼ inch per foot, because it's easier to maintain over a long run and provides better flow. On a 50-foot drain with 2% slope, the outlet end is 12 inches lower than the inlet — a full foot of vertical drop. That's why site grading matters: if your yard is dead flat, you may not have enough fall to make a long drain work without a dry well.
Check slope with a string line and a line level, or use a laser level if you're doing a long run. Mark the trench bottom every 10 feet and verify the drop. It's far easier to fix slope issues while the trench is open than after you've backfilled and discovered the drain doesn't flow.
Permits and utility locates
Most residential French drains don't require a permit if they're simple yard drainage projects that stay on your property and don't tie into municipal storm systems. That said, local rules vary, and some jurisdictions care about any excavation deeper than 18 inches or anything that alters site drainage. A quick call to your building department settles it.
What's non-negotiable is a utility locate. Before you dig anything, call 811 (the national "Call Before You Dig" number) and have your underground utilities marked. It's free, it's required by law in most states, and it keeps you from hitting electric, gas, water, or telecom lines. Utility strikes are expensive, dangerous, and sometimes deadly — the locate call takes five minutes and the flags show up in a day or two. Don't skip it.
A full worked example: 50 linear feet to daylight
Let's walk through a real scenario: you've got a low spot in the side yard that stays soggy after rain. The yard slopes gently toward the street, so you can outlet to daylight at the curb. You want a 50-foot French drain, 18 inches deep, 10 inches wide, running from the wet spot to the street. Contractor install.
| Item | Detail | Cost |
|---|---|---|
| Excavation | Trencher, 50 ft trench, 18″ deep | $400 |
| Perforated pipe | 50 ft × 4″ corrugated + fittings | $75 |
| Gravel | 2.5 cu yd crushed stone, delivered | $120 |
| Landscape fabric | 70 linear ft, 4 ft wide roll | $25 |
| Backfill & grade | Topsoil, compaction, cleanup | $150 |
| Labor | Install, slope verification, fabric wrap | $650 |
| Total | ~$1,420 |
That's about $28.40 per linear foot, right in the middle of the typical range. Add a dry well at the end instead of daylighting and the total climbs to around $2,200–$2,400. Go DIY and you're looking at materials plus a trencher rental, roughly $400–$450 total, but you're trading a weekend for the $1,000 in labor savings.
Run your own length and depth through the French drain calculator to size materials, use the gravel calculator to confirm stone quantities, and if your drainage load is heavy or your soil drains poorly, check the Yard Runoff Calculator to estimate how much water you're actually handling.
Common questions about French drains
How deep should a French drain be?
Most residential French drains are dug 12 to 18 inches deep, which is sufficient to intercept shallow groundwater and handle typical yard drainage. If you're protecting a foundation, dealing with a high water table, or the wet area is large, you may need to go deeper — 24 inches or more. Deeper is generally better for drainage performance, but it costs more to excavate and requires more gravel. The minimum functional depth is about 12 inches; anything shallower won't collect much water and is prone to frost heave in cold climates.
Do the holes in the pipe go up or down?
Holes go down. This is counterintuitive but correct — water enters a French drain from below as the gravel trench fills with groundwater, not from above like a gutter. Perforated pipe with the holes facing down lets water flow in from the bottom and sides. If you install it holes-up, you're relying only on water level rising high enough to enter from the top, which defeats the purpose of the drain. Some pipe is perforated all around, in which case orientation doesn't matter, but if it has a slotted or perforated side, that side faces down.
Can I use PVC instead of corrugated pipe?
Yes, and many pros prefer it. Schedule 40 PVC is more rigid, doesn't crush under backfill, and lasts longer than corrugated plastic pipe. It's also easier to clean if the drain ever clogs. The downside is cost — PVC runs about twice as much per foot as corrugated pipe. For a residential French drain that's properly wrapped in fabric and gravel, either works fine. If you're doing a long run or a deep drain where longevity matters, PVC is worth it.
How long does a French drain last?
A properly installed French drain can last 30 to 50 years or more. The pipe itself is nearly permanent, especially if it's PVC. The limiting factor is usually silt intrusion — over decades, fine soil particles work through the fabric and clog the gravel, reducing flow. This is why landscape fabric and clean crushed stone matter: they slow that process dramatically. Drains installed without fabric or with round river rock instead of angular crushed stone tend to clog within 10 to 15 years. If your drain does clog, it's often cheaper to dig a new one than to excavate and clean the old gravel.
The bottom line
Budget $20 to $50 per linear foot for a professionally installed French drain in 2026, with most standard residential jobs landing around $25–$35 per foot. DIY brings the cost down to roughly $8–$15 per foot in materials plus trencher rental, but you're trading real labor — a 50-foot trench is a full day of work. The keys to a functional drain are proper slope (1–2%), clean crushed stone wrapped in fabric, and perforated pipe laid holes-down.
If you can outlet to daylight, do it — it's simpler and cheaper than a dry well. If not, plan on adding $800 to $2,000 for a dry well tie-in. Size your trench and materials with the French drain calculator, double-check gravel quantities with the gravel calculator, and always call 811 before you dig. A French drain done right solves soggy yard problems for decades; one done wrong is a waste of time and a trench full of mud.