Repair

How to Find a Gutter Leak Before You Call Anyone

By St. Louis Gutter Service · September 11, 2026 · 5 min read

There's water dripping somewhere along the roof edge and you're not sure whether it's the gutter, the roof, or just the rain doing what rain does. Twenty minutes with a garden hose on a dry afternoon will tell you, and you'll be able to describe the problem to whoever you call in a way that gets you a straight price instead of a "we'll have to see."

Three things that look the same from the porch

A leak is water coming through the gutter — a corner, a seam, an end cap, the outlet where the downspout connects, or a pinhole in old steel.

Overflow is water going over the front lip because the gutter can't move it fast enough.

Behind-the-gutter water runs between the gutter and the fascia because the roof edge isn't delivering it into the gutter in the first place.

They cost different amounts to fix and they're fixed by different people. A leak is a $150–$250 reseal. Overflow is a capacity or pitch repair, $150–$300. Behind-the-gutter is a roofing detail — a drip edge — that a gutter crew should point out but a roofer usually installs.

The hose test

Wait for a dry day. You'll need the hose, a helper if you have one, and a spot on the ground where you can see the run in question.

1. Start with the downspout. Put the hose in the top of the downspout (from a ladder on a single story, or drop it in from a window on a two-story where you can). If water backs up out of the top or trickles at the bottom, it's a clog, and everything else you've seen is a symptom of that. Flush it and start over.
2. Fill the run slowly. Set the hose at the far end of the gutter from the downspout, at a trickle. Watch the underside of the gutter. A drip from a corner, an end cap or the outlet within a minute or two, before the gutter is anywhere near full, is a leak. Note exactly where.
3. Turn it up. Open the hose fully. A garden hose delivers roughly a tenth of what a thunderstorm puts on a 30-foot run, so you won't reproduce overflow — but you'll see whether the water moves toward the downspout or sits. Water that pools mid-run and creeps toward the front lip is a pitch problem. Water that reaches the downspout in a steady stream means pitch is fine and any storm overflow is capacity.
4. Check the back. With the hose running, look at the fascia below the gutter. Wet fascia with a dry gutter lip means water is coming from behind — the roof, not the gutter. Stand back and look at the shingle edge: it should overhang the gutter by half an inch to an inch, and there should be a metal strip (the drip edge) visible under the shingles at the eave.

Reading the result

The St. Louis wrinkle

Corners fail here faster than in milder cities because the sealant gets two kinds of abuse: 95-degree July afternoons on the south side, and water freezing in the corner in January. Ten to twelve years is a typical life. If the house was built or re-guttered in 2014 and the corner is dripping in 2026, that's on schedule, not a defect.

Copper is different. A copper half-round on a Tower Grove or Shaw brick home leaks at solder joints, not sealed corners, and the fix is re-soldering, not caulk. If someone has already caulked it, the joint has to be cleaned back to metal before it can be soldered properly. The copper page covers that.

What to tell us when you call

"South-side corner, drips within a minute of the hose going in, fascia below is stained, downspout flows fine." That's a $150–$250 reseal and a fascia look, and we can price it on the phone within a range. Compare that with "there's water coming off the roof somewhere," which gets you a site visit and a shrug. The hose test is what turns the second into the first. When you're ready, the gutter repair page lists each job and its price; if the test showed overflow rather than a leak, why gutters overflow in St. Louis rain is the next thing to read.