Downspouts and drainage in Sioux Falls
In Sioux Falls, roof water can go into the yard, the street or the storm sewer, not the sanitary sewer. The downspouts decide which, and how far from the foundation it lands.
How downspouts should drain
Plan on one downspout for every 30 to 40 feet of gutter. Each downspout should discharge at least 5 feet from the foundation, farther with a basement, onto ground that falls away from the house. City code keeps roof water out of the sanitary sewer without the city engineer’s approval, so the yard, the street and the storm sewer are the allowed routes.
A downspout extension costs about $33 to $40, and a buried line to a pop-up emitter costs $150 to $350 per downspout in 2026.
How many downspouts, and what size
Plan on one downspout for every 30 to 40 feet of gutter, with the gutter sloping toward it at least 1/16 inch per foot. Downspout size follows the roof: about 1 square inch of opening for every 100 square feet of roof. That rates a 2×3 downspout at about 600 square feet and a 3×4 at about 1,200. Whether to go bigger or add one is a separate decision, and gutter width has its own arithmetic.
Where can downspout water go in Sioux Falls?
City code keeps roof runoff, storm water and ground water out of the sanitary sewer unless the city engineer approves it. The city directs sump water to the lawn, the street or the storm system. Keep extensions from crossing a sidewalk or driveway, where the water freezes into ice you have to clear.
Regrading or landscaping in or within 100 feet of the regulated floodplain needs a city floodplain permit. The fee is $75, and review takes about 2 to 4 business days.
Extensions and grading
Downspout extensions should discharge at least 5 feet from the foundation, farther for a house with a basement. A splash block alone moves water only 1 to 3 feet, so pair it with an extension that suits the yard and survives the winter.
The ground matters as much as the pipe. The building code requires the soil to fall at least 6 inches in the first 10 feet from the foundation, and paving within 10 feet to slope away at least 2%. If the yard slopes toward the house, the water follows it.
Buried downspout lines
A buried line moves water farther with nothing to trip over or mow around. Use solid pipe sloped at least 1/8 inch per foot to a pop-up emitter 10 feet or more from the house. Smooth PVC works best, with a cleanout wherever two downspouts join one line.
Buried lines can freeze. Sioux Falls sets footings 42 inches deep to get below the frost, and downspout lines sit well above that. A tee with an overflow grate near the downspout lets water out above ground when the line is frozen, and a small weep hole at the low point lets the emitter drain. Frozen downspouts usually start with meltwater from the roof above.
South Dakota law requires calling 811 at least two business days before digging, including for homeowners. Within 18 inches of a marked line, dig by hand.
Sump pumps and basements
Sump water should discharge at least 20 feet from the house, because water that lands closer can soak back to the foundation. A basement that leaks only after rain almost always has an outside cause. City code also bars sump water that ices a street, alley or sidewalk or runs onto a neighbor’s property. Leave the sump line open to the air where it leaves the house, so water has somewhere to go if the outdoor section freezes.
A rain barrel catches roof water for the garden. Once it’s full, the overflow still needs a path away from the house.
How much does downspout and drainage work cost?
| Job | Price, 2026 |
|---|---|
| Downspout extension | about $33 to $40 each |
| Buried downspout line | $150 to $350 per downspout |
| Underground gutter drainage, whole house | $1,500 to $7,000, average about $2,800 |
A measured quote gives your price.
Before you hire
Get written estimates from more than one company, check proof of insurance, and don’t pay everything up front. Anyone burying a line should call 811 before digging, and a written estimate should say where each downspout will discharge.
Questions about downspouts and drainage
How many downspouts does a house need?
One for every 30 to 40 feet of gutter. A 2×3 downspout drains about 600 square feet of roof, and a 3×4 about 1,200.
How far should downspouts drain from the house?
At least 5 feet, farther with a basement, onto ground that falls away from the house. Buried lines usually end 10 feet or more out, and sump water should land at least 20 feet away.
Can downspouts drain into the sewer in Sioux Falls?
Not the sanitary sewer. City code keeps roof water out of it without the city engineer’s approval. The yard, the street and the storm sewer are the allowed routes.
Should I bury my downspouts?
A buried line moves water farther and clears the lawn, but it can clog and freeze. Use solid pipe with a cleanout, slope it at least 1/8 inch per foot, and call 811 two business days before digging.
Why do buried downspout lines freeze?
They sit well above the 42-inch frost depth Sioux Falls builds footings to, and pop-up emitters can seal with ice. An overflow tee near the downspout lets water out when the line is frozen.
Do I need a permit for drainage work?
The city requires a floodplain permit for grading or building in or within 100 feet of the regulated floodplain. The fee is $75 and review takes about 2 to 4 business days.
What does downspout work cost?
A downspout extension costs about $33 to $40, and a buried line $150 to $350 per downspout in 2026. A measured quote gives the local price.
Related guides
- Gutter installation in Sioux Falls, for sizing
- Gutter cleaning in Sioux Falls, for flushing downspouts
- Why are my gutters overflowing?
- Gutter repair in Sioux Falls
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