How Far Should Downspouts Drain From the House?

At least 4 feet beyond the wall, says University of Minnesota Extension, with the ground sloping away from the foundation at least 1 inch per foot for the first 6 feet. If water still pools or the basement gets wet, the answer is usually more downspouts, longer runs, or piping the water away underground.

The 4-foot rule and why it matters

University of Minnesota Extension says downspout extensions should discharge water at least 4 feet beyond the wall. It also warns that a downspout without an extension or splash block is worse than no downspout at all, because it gathers a whole section of roof and dumps it in one spot against the foundation. The volume is bigger than most people think. Extension notes that 1 inch of rain puts about 1,250 gallons of water on the roof of a 2,000-square-foot house.

Grade: the ground has to help

Even a long extension cannot fix soil that runs back toward the house. University of Minnesota Extension says the ground should slope away from the foundation at least 1 inch per foot for at least 6 feet. Look along your foundation after a storm. Low spots, settled soil near window wells and beds edged so they hold water all send runoff back to the basement wall. Fixing grade is landscaping work, but we will point out where your downspout water is ending up and where it needs to go.

How many downspouts you need

University of Minnesota Extension says to place at least one downspout per 50 linear feet of roof eave. Angi's 2026 guidance is tighter, at one downspout for every 25 to 35 feet of gutter and no more than 40 feet between them. Size counts too. This Old House rates a 2x3 downspout at about 600 square feet of drainage area and a 3x4 at up to 1,200. On many homes, adding one outlet at a problem corner solves overflow and the wet spot below it.

Splash blocks, extensions and flip-ups

The simplest fix is a splash block or an extension that turns the water out over the lawn instead of into a bed. HomeAdvisor's 2026 data puts splash blocks at about $10 each and downspout screens at about $8 each. Those are national market prices, and your actual price comes from a free estimate. We also install downspout hinges and flip-ups, so a long extension lifts out of the way for mowing and drops back down before the next rain. Extensions only work if they stay attached.

Underground tile and pop-up emitters

When an extension would cross a sidewalk, driveway or patio, the downspout can be piped away underground. A diverter at the bottom of the downspout feeds buried pipe that runs downhill to a pop-up emitter in the yard, where water bubbles out and the lid drops shut. Flow Right installs underground tiling and diverters along with the gutters. Buried lines need a steady fall and a clear outlet, and the gutters above them need to stay clean so leaves do not plug the pipe.

Where the water may go

Des Moines and each suburb set their own rules about where downspout and sump water may discharge. We have not confirmed those rules city by city, so check with your city before you send water toward a street, a sidewalk or a neighbor's yard. Keep water off walkways where it can freeze in winter. In most yards the goal is simple: get the water out past the 4-foot mark onto ground that falls away from the house and away from the neighbors.

Why Central Iowa storms test downspouts

Des Moines averages 36.55 inches of precipitation a year under the National Weather Service's 1991 to 2020 normals, and much of it arrives in hard bursts. Iowa's stormwater design manual lists a 100-year, 5-minute rainfall intensity of 12.4 inches per hour for its Central Iowa section. In a burst like that, a single 2x3 downspout at the far end of a long run cannot keep up. Our downspout and drainage work sizes outlets for the storm, not the average day.

Common Questions

What to Do Next

If you have a wet basement corner or a downspout dumping into a bed, call or text Luke at (515) 901-3646 or send our estimate form. He will trace where the water goes and show you the fix, from a flip-up extension to underground tile.

See our downspouts & drainage service or call or text (515) 901-3646.