Yard drainage and French drains

A good deal of basement water begins as roof and yard water that was never led away from the house. Dealing with it outdoors is often the least disruptive place to start.

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A yard seen from the side, falling away from the house on the left. Roof water comes down the grey downspout into a buried green pipe and runs to the stone-filled pit near the street. The stone trench in mid-yard, with a ringed pipe at its bottom, is the French drain: surface water (blue arrows) reaches it from both sides and sinks through the stone into the pipe.

Three pieces that do most of the work

Downspout lines

Each downspout is joined to a solid buried pipe that carries roof water well clear of the foundation before letting it go. A roof sheds a surprising volume in one storm, all of it at the corners of the house.

Grading

Soil is added and shaped so the ground falls away from the walls on every side, without burying the siding. Paving that tilts toward the house is relaid or cut and drained.

A French drain

A trench lined with filter fabric and filled with stone around a perforated pipe. It gathers water moving across or through the ground and gives it an easy path to somewhere harmless.

The hard part: where the water ends up

On a small lot, collecting water is easy and getting rid of it is not. The usual outlets are a dry well, which is a buried stone pit or plastic chamber that lets water soak away, or an outlet that opens on a lawn with room to spare.

It must not be sent onto the next property, and it should not run over a sidewalk, where it turns to ice in winter. A pipe through the curb or into a catch basin is a question for Clifton's Engineering Department, which issues the permits for sidewalk, curb and street-opening work.

What it does to the yard

Expect narrow trenches across the lawn and through planting beds, dug by a small trencher or by hand. Tree roots, sprinkler pipes and buried cables all slow the work. The trenches are refilled and seeded, and the lines show for a season.

Buried utilities have to be marked before any of it starts. New Jersey requires a request to New Jersey One Call on 811 at least three full business days before digging.

Questions that separate a design from a guess

How much fall does each pipe have, end to end?
Where does solid pipe change to perforated, and why there?
Is the trench wrapped in filter fabric so silt cannot clog the stone?
How big is the dry well, and what happens when it is full?
Are there cleanouts where the downspouts join the buried line?
Who restores the lawn and the beds?

Yard drainage questions

Will a French drain in the yard dry my basement?

If the water is coming from the surface, it can. If the water table itself rises under the floor in wet seasons, a yard drain will not lower it, and the house needs drainage indoors.

Are plastic splash blocks and flexible extensions enough?

They are a fair first test. Run every downspout several feet out for a month of rain and see what changes indoors. If the basement improves, burying proper lines is money well aimed.

Can the downspouts be connected to the sewer?

Not in Clifton. The city's sewer chapter does not allow roof downspouts to be joined to a building sewer that leads to the sanitary sewer. See the discharge guide.