How much does a French drain cost per foot?

One national cost guide lists a shallow exterior French drain at $10 to $35 per linear foot. Another lists exterior drains at $10 to $65. A deep drain down at the footing runs $30 to $90 per foot in the first guide. That guide ties the price to length, depth, materials and access.

What is the difference between a French drain and a curtain drain?

A surface French drain mostly moves surface water from where it gathers to an outlet. A curtain drain sits deeper and catches groundwater before it reaches a house or a wet part of the yard. One national guide sets curtain drains at 2 feet deep or more, covered with soil.

How much does a dry well cost?

Published dry well prices run $500 to $3,000 in one national guide and $1,200 to $5,200 in another. A third puts it at $1,500 to $5,000. Size and soil drive much of that spread. Rhode Island's single-family stormwater guidance sizes a dry well for the first inch of roof runoff.

Do I need a permit for a French drain in Rhode Island?

It depends on the town and the site, so start with the town building office. RIDEM exempts a house lot from stormwater registration when it soaks its own runoff into the ground. The project must drain less than 10,000 square feet of roof and paving. Work near a wetland or the shore may need RIDEM or CRMC review.

Can a French drain tie into my sewer line or septic system?

No. Rhode Island's plumbing code says storm water shall not drain into a sewer meant for sewage only. The state's septic rules bar subsurface drains from discharging into a septic system. The drain needs its own outlet, such as daylight on lower ground or a dry well.

How long does a French drain last?

One national cost guide says most French drains last 30 to 40 years or more when installed correctly. It notes shorter lifespans in sandy soil and in areas with heavy plant growth. The same guide favors filter fabric around the stone to prevent clogging.

Is this what South County Septic charges?

No. These are published market ranges from national cost guides, not our price list. We look at the job and put the quote in writing, because the ground and the outlet change the work. Call or text (401) 474-8926.

How much does a French drain cost in Rhode Island?

A shallow exterior French drain costs $10 to $35 per linear foot in one national cost guide. Another guide puts exterior French drains at $10 to $65 per foot. A 100-foot run comes to $1,000 to $3,500 in the first guide and $1,000 to $6,500 in the second. Two guides put the average job near $5,000.

Those are market numbers, not our price list. In Rhode Island, a high water table or ledge can push a job up the range. So can a long run to the outlet. When a yard stays wet, a French drain or a curtain drain can carry the water away.

What do the cost guides publish for each kind of drain?

Each letter in the table is a different national cost guide, read in October 2026. Every range is for installed work.

Drainage work	Per linear foot	Whole job	National cost guide
Surface-level French drain in a yard	$10 to $30	$500 to $5,300	A
Curtain drain or shallow French drain	$10 to $35	$1,500 to $8,800	A
Exterior French drain	$10 to $65	$1,000 to $6,500 for 100 feet	B
Deep drain at the footing, one side of a house	$30 to $90	$1,200 to $4,500	A
Curtain drain	$10 to $25	$1,000 to $2,500	C
Dry well	not given	$1,200 to $5,200	A
Dry well	not given	$500 to $3,000	B
Dry well	not given	$1,500 to $5,000	C

The spread is wide because each range covers many kinds of yards. Labor carries most of the bill, guide A notes, so the dig sets the price more than the pipe does.

Why does the water table matter so much in Rhode Island?

NOAA’s 1991 to 2020 normals put Kingston, in South Kingstown, at about 53 inches of precipitation a year. Where that water goes depends on the soil, and the soil changes from town to town.

North Kingstown’s most common soil is Merrimac, a sandy outwash soil. USDA soil data record no water table within about 6.5 feet of the surface in it. Ground like that soaks water away, and a dry well has room to work.

Narragansett’s most common soils formed in dense till, a packed layer many people call hardpan. In Rainbow soil, USDA data put the seasonal high water table about 2 feet down. In Stissing, it rises within a foot of the surface. A drain has to sit low enough to catch that perched water, and deeper trenches cost more per foot.

That perched water is what a curtain drain is built to catch. A dry well is a poor match for it. Rhode Island’s single-family stormwater guidance sets a dry well’s bottom at least 2 feet above the seasonal high groundwater table. The same guidance notes that an older septic system plan may already show that depth.

What happens when the trench hits ledge?

Ledge is the New England word for bedrock near the surface. USDA’s soil survey maps more than 70,000 acres of Rhode Island as very rocky soils or rock outcrop. Several of the state’s largest soil units are also rated very stony or extremely stony.

A national trenching cost guide says digging costs more in rocky soil. It prices boulder and ledge removal as its own line, on top of the trench.

When a line meets ledge, the drain goes around it or the rock gets broken out. Going around adds pipe, and breaking rock adds machine time. Ledge calls for excavation and trenching machines, so ask how each bid handles it.

Where does the water go, and why does the outlet cost money?

A French drain needs somewhere lower to send its water, unless the soil soaks it up fast. Guide A calls for a slope of at least 1 percent, or 1 foot of drop per 100 feet. On a flat lot, the pipe may run a long way to reach the surface, and that adds trench.

Rhode Island’s plumbing code lists where a subsoil drain may discharge. The choices are a trapped area drain, a sump, a dry well or an approved spot above ground. The same code says storm water shall not drain into a sewer meant for sewage only. That rules out the house sewer line.

On a septic lot, Rhode Island’s septic rules bar subsurface drains from discharging into the system. They also keep subsurface and foundation drains 15 to 50 feet from septic parts. The slope sets which distance applies.

The state’s stormwater guidance keeps a dry well 15 feet from a septic system and 10 feet from a building. A private drinking water well gets 50 feet.

A tie-in to a street storm drain needs permission from whoever owns the road. The Rhode Island Department of Environmental Management (RIDEM) oversees freshwater wetlands. Its permit zone reaches 200 feet from a river or stream and 100 feet from other freshwater wetlands. Wetlands near the coast fall to the Coastal Resources Management Council (CRMC).

Before machine digging near utility lines, state law requires a Dig Safe notice (call 811) at least 72 hours ahead. Weekends and holidays do not count. Dig Safe members do not mark private lines, such as sprinkler pipes.

When does regrading cost less than a French drain?

If water runs across the surface toward the house, the grade is the problem. Rhode Island’s residential code calls for at least 6 inches of fall in the first 10 feet from a foundation. Where walls or lot lines block that slope, the code calls for drains or swales.

The published numbers for regrading run lower. Guide A puts yard regrading at $500 to $5,000, against $1,500 to $8,800 for a curtain drain. Another national guide puts regrading at a foundation at $835 to $3,000.

Sometimes the wet spot is just roof water. Guide A prices an underground downspout line at $150 to $350 per downspout.

Grading handles surface water. Groundwater that seeps up from below is curtain drain work. Some yards need both: grading and site work for the surface, and a short drain for the one spot that stays wet.

Is that wet spot a drainage problem or a septic problem?

On a septic lot, check where the wet spot sits. EPA lists standing water or damp spots over a leach field as a sign of septic failure. Sewage odor near the leach field points the same way. A failing leach field is a septic system repair question first.

What should a written drainage quote include?

A written quote should spell out these items:

the length and depth of each drain
the outlet, and the pipe run to reach it
how ledge or boulders get handled
where the spoil goes, and the lawn repair after the trench

Guide A notes that reusing trench soil on site cuts disposal fees. Hauling it away adds to the bill.

How do you get a drainage quote in South County?

South County Septic and Excavation Services builds French drains, curtain drains, footing drains and dry wells across Rhode Island. North Kingstown sits at the center of our service area. We look at the job and put the quote in writing. Call or text (401) 474-8926, or read more on our drainage systems page.