Case file — North Potomac, Montgomery County, MD. One of 79 projects we completed across the DMV in 2025. New here? Start with our open letter.
At a glance
| Location | North Potomac, Montgomery County, MD |
| The problem | The front yard turned into a pond after every storm |
| Real cause | The house sits below road grade — runoff had nowhere to go but toward the home |
| The fix | Exterior French drain: graded and compacted trench, geotextile wrap, #57 stone, 6″ perforated pipe, catch basin, gravity discharge to the rear yard |
What the homeowner saw
Every heavy rain, the front yard filled up. Not a damp patch — standing water, wide enough that the owners described it as a lake sitting between the walkway and the house. It would linger for hours after the rain stopped, killing the grass and putting water right up against the foundation.
What we found
The problem wasn’t the foundation. It was elevation.
This house sits below the grade of the road. That single fact drives everything. Water always moves downhill, and on this lot the lowest point in the path was the front yard. Runoff coming off the street and the uphill ground didn’t have to find its way to the house — gravity delivered it there. Every storm, the yard was doing the job of a catch basin, just without the pipe.
That’s why regrading alone wouldn’t have solved it, and why nothing sealed to the foundation would have either. You cannot stop water that the site itself is aiming at the house. You have to give it a faster path than the one it’s already taking.
The good news was that the lot had somewhere to send it. The natural fall of the property continued past the house toward the rear yard — open ground, well away from the foundation. We didn’t need a pump or a tie-in. We needed to intercept the water in front and let gravity finish the job.
What we did
We installed an exterior French drain along the front of the property, sized and built to carry real storm volume — not a decorative gravel line.
- Excavated the trench along the line where the water was collecting, in front of the walkway, with the lawn tarped and the work area fenced off.
- Graded the trench bottom to a consistent fall and compacted it with a plate compactor. This is the step that decides whether a French drain works for twenty years or two. A trench bottom that dips — or that settles later because it was never compacted — turns the drain into a holding tank. We set the slope and checked it with a straightedge before a single stone went in.
- Lined the trench with geotextile fabric, wrapped up both sides. The fabric lets water pass but keeps soil fines out of the stone. Without it, silt migrates into the voids and the drain slowly chokes itself — the most common reason a French drain stops draining after a few seasons.
- Set 6″ perforated pipe on a bed of #57 washed stone, following the grade we’d established, then covered it with more #57 and closed the fabric over the top — a full “burrito” wrap.
- Installed a catch basin on the line to take surface water directly, so ponding at the low spot is captured before it ever spreads across the yard.
- Discharged to the rear yard by gravity, following the property’s natural fall — no pump, nothing to fail, nothing to maintain.
- Restored the surface — the flagstone walkway reset with its river-rock border, and the disturbed lawn regraded and strawed.
Our own crews did all of it. No subcontractors.
The trench, cut along the line where the water was collecting in front of the walkway.
Our own crew, staging the stone. No subcontractors on this job.
Geotextile fabric lining the trench and wrapped up both sides — the step that keeps soil fines out of the stone.
Checking the fall with a straightedge before a single length of pipe went in. Get this wrong and the drain becomes a holding tank.
6″ perforated pipe on a bed of #57 washed stone, fabric open and ready to close over the top.
The catch basin on the line, taking surface water directly before it can spread across the yard.
The flagstone walkway reset with its river-rock border once the line was closed up.
The result
The photograph we care about most is the one taken in the rain, after the work was done. The ground is wet, the walkway is wet — and there is no pond anywhere. The same storm that used to leave a lake between the walkway and the house now runs through the drain and off the property. The front yard drains instead of collecting, and the water that used to sit against the foundation leaves the way the site always wanted it to go.
Taken in the rain after completion: straw down on the restored lawn, and not a puddle in sight.
The takeaway
When a house sits below the road, standing water in the yard isn’t a landscaping problem — it’s a hydraulics problem, and no amount of topsoil or sealant fixes it. What fixes it is a drain with real slope, real stone, and a fabric wrap, discharging somewhere gravity already wants to take the water. Skip the slope and the compaction and you haven’t built a drain; you’ve buried a bathtub.
Is your yard holding water after every storm? Schedule a free inspection — we’ll read the grade, find where the water is actually coming from, and tell you honestly what it takes to move it. Learn more about our yard drainage work.
FAQ
Why do some French drains stop working after a few years?
Two reasons, almost always. First, no filter fabric — soil fines wash into the stone and clog the voids until water can’t move through. Second, no compaction under the pipe, so the trench bottom settles unevenly and creates low spots that hold water instead of carrying it. Both are invisible once the trench is backfilled, which is exactly why they get skipped.
Can’t I just regrade the yard instead?
Sometimes — if the lot has somewhere higher to push water from and somewhere lower to send it. But when the house sits below the road, regrading has nothing to work with: the water is arriving from above no matter what you do at the surface. In that situation you need to intercept it underground and pipe it past the house.
Written by S. Altan Atasoy — civil engineer (University of the District of Columbia), a member of the American Society of Civil Engineers, and MHIC-licensed in Maryland (#165773) — in the field since 2005.
