Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Total drain cost
$1,530
Trenching labor
$840
Discharge outlet cost
$150
All-in cost per linear foot
$25.50
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter drain length (linear ft).
- 2Enter pipe, gravel & fabric rate ($/ft).
- 3Enter trenching labor rate ($/ft).
- 4Enter discharge outlet type.
- 5Read your total drain cost on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
A French drain moves surface and groundwater away from a foundation or low spot using a perforated pipe bedded in gravel and wrapped in filter fabric inside a sloped trench. Cost scales almost entirely with linear footage, since trenching labor is the dominant cost driver, followed by pipe, gravel backfill, and fabric material. 2026 US national averages run roughly $10-$25 per linear foot for a standard interior or shallow exterior French drain, with deep exterior drains along a foundation running $25-$50 per foot due to more extensive excavation and often the need to daylight to a discharge point or connect to a sump pit. This calculator multiplies your linear footage by a combined material rate and adds trenching labor, then flags a pop-up emitter or sump connection cost if selected. Get a soil test or contractor site visit before finalizing a French drain plan — rocky or clay-heavy soil can significantly increase trenching labor time and therefore total cost.
Worked example
Using the values the calculator loads with:
Inputs
- Drain length: 60 linear ft
- Pipe, gravel & fabric rate: 9 $/ft
- Trenching labor rate: 14 $/ft
- Discharge outlet type: Pop-up emitter — +$150
Results
- Total drain cost: $1,530
- Trenching labor: $840
- Discharge outlet cost: $150
- All-in cost per linear foot: $25.50
What each field means
Inputs
- Drain length (linear ft)
- The drain length used in the calculation, measured in linear ft. Starts at 60 linear ft so you have a working example on load. Accepted range: 10–400 linear ft.
- Pipe, gravel & fabric rate ($/ft)
- The pipe, gravel & fabric rate used in the calculation, measured in $/ft. Starts at 9 $/ft so you have a working example on load. Accepted range: 4–20 $/ft.
- Trenching labor rate ($/ft)
- The trenching labor rate used in the calculation, measured in $/ft. Starts at 14 $/ft so you have a working example on load. Accepted range: 5–35 $/ft.
- Discharge outlet type
- Pick the option that matches your situation — the maths changes per option. Choices: Pop-up emitter — +$150, Tie into sump pit — +$450, Daylight to grade — +$50.
Results
- Total drain cost
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Trenching labor
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Discharge outlet cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- All-in cost per linear foot
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
French drain vs. sump pump — which do I need?
A French drain redirects water via gravity before it reaches the foundation, while a sump pump actively removes water that's already collected in a pit; many homes use both, with the drain feeding water to the pit for the pump to discharge.
How deep does a French drain need to be?
Exterior foundation drains are typically dug alongside the footing, often 1-3 feet deep, while interior drains along a basement's perimeter are usually shallower. Depth depends on your local frost line and the source of the water problem.
Does a French drain need ongoing maintenance?
Yes — the gravel and pipe can silt up over 10-15 years, especially without proper filter fabric, so periodic inspection of the outlet and occasional flushing helps the system keep working as designed.
Can I install a French drain myself?
Simple surface drains for a small low spot are DIY-feasible, but foundation-adjacent French drains involve grading calculations and connection to existing drainage that most homeowners hire out to avoid redirecting water into, rather than away from, the foundation.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). French Drain Installation Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/french-drain-installation-cost
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/french-drain-installation-cost" target="_blank" rel="noopener">French Drain Installation Cost Calculator — RevenueLab</a> (2026).</p>
Source: [French Drain Installation Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/french-drain-installation-cost) (2026).