Case file — Gaithersburg, Montgomery County, MD. One of the 25 jobs in our 250-home series. New here? Start with our open letter.
At a glance
| Location | Gaithersburg, Montgomery County, MD |
| The problem | Surface water crossing the property with nowhere to go |
| The fix | About 100 feet of yard French drain, two catch basins, and full restoration of the lawn over the whole run |
| Why it is here | Because it shows where the money in a drainage job actually goes |
Everybody thinks they are buying pipe
Ask a homeowner what a French drain is and you will hear some version of “a perforated pipe in the ground.”
That is true, and it is also why drainage quotes feel outrageous. A hundred feet of 4-inch perforated pipe is not an expensive object. If that is what you think you are buying, every quote you receive will look like a markup.
So here is where the money went on this job, as a share of the total.
| Part of the job | Share of the cost |
|---|---|
| Gravel, supplied, placed and compacted | Roughly 30% |
| Excavation and hauling the soil away | Roughly 29% |
| Putting the yard back — grass or mulch over the full run | Roughly 24% |
| The perforated pipe itself | Under 10% |
| Two catch basins | Roughly 8% |
The pipe is the smallest line on the list except the basins. Nine dollars in ten went to moving material and to leaving the property looking like nobody had been there.
Digging is the job
The trench on this run is a foot wide and a foot and a half deep, for about a hundred feet, cut to a consistent fall so water actually moves.
Then the soil leaves. It does not get piled at the end of the yard — it is loaded and hauled to a dump station, which is a cost per load and a cost in time. On a hundred-foot run that is real volume.
People underestimate this because they have dug a hole in a garden before. Digging a hundred feet of trench to a controlled slope, in DMV clay, and taking the spoil away is not that activity at a larger scale. It is a different activity.
Gravel is the system
Nearly a third of the cost is stone, and it is the part most likely to be quietly reduced on a cheaper quote.
The gravel is what makes the trench work. It holds open voids for water to travel through, it protects the pipe, and it has to be placed and compacted properly or the ground above it settles into a trough. Use less of it, or use a dirtier grade, and the drain still exists — it just moves less water, and it silts up sooner.
This is the easiest place in all of drainage to save money invisibly. You cannot see it from the surface once it is done.
Restoration is a quarter of the bill, and it is not optional
Almost a quarter of this job was putting the yard back: grass seed or sod, or mulch, over the entire hundred-foot run, after backfilling and cleanup.
Two reasons it belongs on the invoice rather than on the homeowner’s weekend.
The honest one: a hundred-foot scar through a lawn is real damage, and leaving it is leaving the job unfinished.
The practical one: bare soil on a fresh trench line erodes. The first hard rain moves it, the fill settles unevenly, and the trough that forms is exactly the channel you were trying to eliminate. Vegetation holds the surface while the ground knits back together.
If a quote is noticeably cheaper than the others, check whether restoration is in it. Very often it is the missing quarter.
The catch basins
Two 12-inch basins, set in prepared excavation, connected into the line and surrounded by gravel.
A French drain collects water that is in the ground. A catch basin collects water that is on top of it — the low spot that puddles, the place where runoff arrives faster than soil can take it. Most real yards need both, which is why the North Potomac yard in this series got one too.
What to do with this
Next time you compare drainage quotes, stop comparing the pipe.
Ask how deep and how wide the trench is, what happens to the spoil, what grade of stone and how much of it, and what condition the yard is left in. Those four answers are about ninety percent of what you are paying for, and they are where two quotes that look similar turn out not to be.