Two questions come up on almost every site visit in Springfield, Annandale, and Burke when drainage is part of the scope: "Do I need a French drain or a dry well?" and "Why does my neighbor's drainage solution not work?" The honest 2026 answer is that the choice depends on where the water is coming from, where it can go, and what the underlying soil will accept — and Northern Virginia clay soil constrains the answer in ways most drainage articles do not address.
I'm Nelson, owner of Kaeler. We have installed both systems across NoVA for almost two decades. This is the breakdown of when each one works, when each one fails, and the hybrid approach we use most often on Springfield and Annandale clay.
The short answer: which to pick in NoVA
| Use case | Best solution | Why |
|---|---|---|
| Sheet flow off a slope | French drain | Captures and redirects continuous flow |
| Roof gutter / downspout concentration | Dry well (if soil percolates) OR pipe to daylight | Volume in pulses, needs storage or discharge |
| Sheet flow + no daylight available | French drain to dry well | Hybrid — collect, store, slow-release |
| Heavy clay with no percolation | French drain to daylight only | Dry wells fail in true NoVA clay |
| Patio base saturation | French drain along uphill edge | Intercepts before reaching base |
| Soggy yard general | Yard regrading + French drain combo | Depends on grade availability |
The "heavy clay with no percolation" row is the one that surprises most homeowners. In Springfield, Annandale, and Burke, the clay below the topsoil can absorb water at less than 0.1 inches per hour. A standard dry well sized for percolating soil simply does not drain — it becomes a buried bucket that fills and stays full.
What a French drain actually does
A French drain is a perforated pipe in a stone-filled trench, wrapped in filter fabric, daylighted to a low point. It intercepts groundwater and sheet flow, gathers it into the pipe through perforations, and moves it laterally to wherever you want the water to end up.
| Component | Spec on a proper Kaeler install |
|---|---|
| Trench depth | 18–24 inches |
| Trench width | 12–18 inches |
| Stone | Washed VDOT #57 (1/2 to 1 inch) |
| Pipe | 4-inch perforated PVC (not corrugated, never sock-only) |
| Filter fabric | Non-woven geotextile, wraps stone and pipe |
| Slope | Minimum 1% (1 inch drop per 8 feet) |
| Outflow | Daylighted to grade, pop-up emitter, or dry well |
2026 NoVA installed pricing: $40 – $75 per linear foot. A typical 30 ft French drain along the uphill edge of a patio: $1,200 – $2,250.
Where French drains work great
- Sheet flow off a slope
- Wet basement caused by lateral groundwater flow against the foundation
- Along the uphill edge of a patio or hardscape
- Capturing seasonal high water table
Where French drains fail
- No place for the outflow to daylight (the drain has nowhere to send water)
- Trench too shallow (less than 12 inches deep — water finds an easier path)
- Slope too flat (less than 1% pitch — water sits in the pipe)
- Pipe is "sock pipe" laid in dirt without stone — the filter fabric clogs within 2–3 years
- Trench backfilled with native clay instead of stone — water cannot reach the perforations
The most common failure we see in NoVA is #5: native clay backfill. A contractor digs the trench, lays the pipe, and shovels the dirt back on top. The clay seals the trench, water flows over the top, and the drain does nothing.
What a dry well actually does
A dry well is a buried chamber (either a plastic cube/cylinder structure or a stone-filled pit) that collects water and stores it temporarily, allowing it to percolate into the surrounding soil over hours or days.
| Component | Spec on a proper Kaeler install |
|---|---|
| Chamber type | Pre-fab plastic dry well (Flo-Well or NDS), 4×4×3 ft typical |
| Stone surround | 6 inches washed VDOT #57 on all sides |
| Inflow | 4-inch solid PVC from downspout or capture point |
| Outflow (if percolation insufficient) | Overflow pipe to daylight or secondary dry well |
| Depth | Top of chamber 12–18 inches below grade |
2026 NoVA installed pricing for a pre-fab dry well: $1,800 – $4,400 depending on size, excavation, and inflow piping.
Where dry wells work great
- Soils that percolate well (sandy loam, sandy clay loam — uncommon in NoVA)
- Lots with no available daylight point for a French drain
- Catching downspout discharge in pulses (high volume, short duration)
- HOA neighborhoods that prohibit surface drainage discharge
Where dry wells fail
- True clay soil with percolation under 0.3 inches per hour (most of Springfield, Annandale, Burke)
- Sized too small for the contributing roof area
- Installed below the seasonal high water table (water table fills the dry well, not the rainfall)
- No filter / no debris cap on inflow — leaves and grit clog the chamber
- No overflow plan — when the dry well fills, water surfaces wherever it can find air
The most common failure mode in NoVA: dry well installed in heavy clay, soil cannot percolate the design volume, water backs up into the contributing downspout, then overflows at the foundation — often making the basement situation worse than before the dry well was installed.
How to test which solution your soil supports
Before committing to a dry well in NoVA, the right move is a percolation test:
1. Dig a test hole at the planned dry well location — 12 inches deep, 12 inches wide. 2. Fill with water and let it drain. Confirms the hole is not sitting in standing groundwater. 3. Refill the hole to a marked depth (typically 12 inches from the bottom). 4. Measure the drop over 1 hour. Calculate inches per hour.
| Result | Recommended solution |
|---|---|
| Over 1.0 in/hr | Dry well is great |
| 0.5 – 1.0 in/hr | Dry well with larger chamber + overflow plan |
| 0.2 – 0.5 in/hr | Dry well marginal; French drain preferred |
| Under 0.2 in/hr | Dry well will fail; French drain to daylight only |
Most heavy clay lots in Springfield, Annandale, and Burke test at 0.05–0.15 in/hr. That is the "dry well will fail" range.
The hybrid: French drain INTO a dry well
For lots that cannot daylight a French drain (no low point on the property, HOA prohibits surface discharge, etc.) the right solution is often a French drain feeding a properly-sized dry well with an overflow.
How it works:
1. French drain captures sheet flow / uphill groundwater along the wet edge of the lot. 2. Solid PVC pipe carries the captured water to a buried dry well chamber. 3. Dry well stores the water and slowly percolates it into surrounding soil. 4. Overflow pipe carries any excess to a secondary outflow — pop-up emitter, secondary dry well, or daylight at the property line.
2026 NoVA installed pricing for this hybrid: $3,400 – $7,200 for a 30 ft French drain feeding a single dry well with overflow.
This is the approach we use most often in Springfield neighborhoods where the lot slopes toward a fence line but there is no easement to discharge to.
Pricing comparison summary
| Solution | 2026 NoVA installed cost | Typical use |
|---|---|---|
| French drain to daylight (30 ft) | $1,200 – $2,250 | Slope + low point available |
| Pre-fab dry well (4×4×3 ft) | $1,800 – $4,400 | Downspout capture in percolating soil |
| French drain to dry well hybrid | $3,400 – $7,200 | Capture + storage with no daylight |
| Yard regrading + surface emitter | $1,800 – $4,800 | Surface flow, no buried system needed |
| Full perimeter foundation drain | $9,500 – $24,000+ | Basement waterproofing scope |
For deeper context on choosing drainage approaches for hardscape projects specifically, see our piece on drainage solutions in Northern Virginia clay soil and why drainage has to be installed before a patio, not after.
What we install most often in each NoVA city
| City | Most common drainage scope |
|---|---|
| Springfield (22150, 22151) | French drain to daylight (clay, generally has fence-line slope) |
| Annandale (22003) | French drain to dry well hybrid (clay, often no daylight) |
| Burke (22015) | French drain to daylight (sloped lots) |
| Fairfax (22030, 22031) | Mix — depends on lot |
| McLean (22101, 22102) | Pre-fab dry well + downspout extension (better-drained loam) |
| Vienna (22180) | Yard regrading + French drain combo |
If you have a specific drainage problem on a specific lot, book a free site visit and we will diagnose on the lot before quoting.
Frequently asked questions
Can I install a dry well in NoVA clay soil?
Sometimes — depends on actual percolation test results. In the Fairfax County clay belt (Springfield, Annandale, much of Burke), a percolation test usually rules out dry wells. In better-drained pockets (parts of McLean, Great Falls, higher elevations), dry wells work fine.
Do I need a permit for a French drain in Fairfax County?
If the drain ties into the county storm sewer or discharges within a storm-water easement, yes — and the design must meet county spec. A French drain discharging onto your own property to a pop-up emitter does not require a permit. We confirm during the site visit.
How long does a French drain last?
A properly installed French drain (correct depth, stone backfill, geotextile-wrapped pipe, daylighted outflow) lasts 30–50 years in NoVA. Failure usually comes from clogged filter fabric or root intrusion, both of which are slow.
How long does a dry well last?
A pre-fab plastic dry well with proper inflow filtering lasts 20–40 years. Failure modes: chamber sediment buildup (mostly from un-filtered inflow) and gradual clogging of the surrounding stone surround.
Is corrugated drainpipe okay for a French drain?
We do not use corrugated black pipe on French drains in NoVA. Corrugated pipe is harder to clean, easier to crush under load, and the ridges trap sediment. Smooth-wall perforated PVC lasts longer and performs better.
Can I retrofit drainage after a patio fails?
Yes, but it is significantly more expensive than installing it before — and the patio sometimes needs partial rebuild to integrate the new drainage. See our piece on why drainage has to come before the patio for the full cost comparison.
Ready to scope your drainage?
If your yard has standing water, your basement is wet, or your patio is starting to heave — book a free drainage site visit and we will diagnose the cause and propose the right solution before quoting.
We solve drainage problems across Springfield, Annandale, Burke, Fairfax, and the rest of the 18 NoVA cities we serve. See all areas we serve.
