Sizing and count
Standard is a 2x3 downspout on 5-inch gutter and a 3x4 on 6-inch. A 3x4 moves a little over twice the water of a 2x3, which matters more than most people expect.
Count matters as much as size. The working rule is one downspout for roughly every 30 to 35 feet of gutter, and more where a big roof plane funnels into one spot. We see plenty of homes where adding a second drop fixed an overflow that a bigger gutter wouldn't have.
Where the water goes
Six feet from the wall is the minimum we're comfortable with, and ten is better on a flat lot. An elbow and a splash block at the slab does almost nothing except move the puddle three inches.
On a graded lot, a solid extension out to where the ground falls away is usually enough. On flat North County lots or hillside sites in Fenton and Sunset Hills, buried line is the real answer.
Buried drain lines
We trench, lay solid PVC — not corrugated black pipe, which crushes and holds sediment — and run it out to daylight or a pop-up emitter at a low point.
Solid pipe with a proper fall and a cleanout can be rodded out if it ever needs it. Corrugated line buried at a shallow depth is a repair somebody makes in ten years.
The signs you have a discharge problem
A trench worn into the mulch under one downspout. Efflorescence or a damp line on the basement wall on that same corner. Mud splashed up the siding two feet. A section of settled sidewalk right below an elbow.
Those all point at the same thing, and none of them are fixed by cleaning the gutter.
Questions people ask
How far should a downspout discharge from the house?
Six feet minimum, ten if the lot is flat. The goal is past the backfill zone, where the soil is looser and water finds its way down the wall.
Can you bury my downspouts?
Yes. We use solid PVC with a proper fall, out to daylight or a pop-up emitter, with a cleanout so it can be serviced.
How many downspouts do I need?
Roughly one per 30 to 35 feet of gutter, adjusted for roof area feeding that run. Wide roof planes need more.
Will a bigger downspout fix my overflowing gutter?
Sometimes. If the trough is overflowing at one end, it's often the number of drops rather than their size. We look at the whole run before recommending either.
Do you connect downspouts to an existing underground line?
We can, once we've checked the existing line still flows. Old collapsed lines get replaced rather than tied into.
Free estimate
We measure, we look at the fascia, and you get a number in writing.
Talk to a real St. Louis gutter company
Third generation, family-run since 1947. Somebody picks up, day or night.