How to Find a Gutter Leak Before You Call Anyone
A lot of "gutter leaks" in San Antonio aren't leaks. They're overflow, water running behind the gutter, or a roof problem that shows up at the gutter line. The other half are real, and they're almost always at a corner, an end cap or an outlet. You can tell which you've got with a garden hose and twenty minutes on a dry afternoon, and it changes what you ask for when you call.
What you'll need
A garden hose long enough to reach the roofline, a ladder if the house is single-story and you're comfortable on one, and someone to stand on the ground and watch. On a two-story house, skip the ladder and do the ground-only version at the end.
Step one: read the evidence before adding water
Walk the house and look at the ground and the walls under the gutter. What you're looking for:
- A drip stain or clean spot on the ground directly under a corner or end cap. That's a joint leak.
- A green or dark streak down the wall from a spot on the gutter. Also a joint leak, or an outlet leak if it's under a downspout.
- A scoured line in the mulch along a whole run, or mud splashed on the wall along a length. Overflow, not a leak.
- Water stains, peeling paint or dark rot on the fascia board behind the gutter. Water running behind the gutter, which is a roof-edge problem.
- Stains on the soffit (the underside of the eave) or on the ceiling inside near an outside wall. Could be either behind-the-gutter water or a roof leak. Note where.
Write it down or take photos. Then get the hose.
Step two: the hose test, one run at a time
Start at the far end of a run, away from the downspout. Put the hose in the gutter at a moderate flow — not full blast — and let it run for two minutes while your helper watches from the ground.
Water drips from a corner, end cap or the outlet within a minute or two. That's a joint leak. It's a clean-and-reseal repair, $150–$250, and the sealant on the other joints is the same age, so it's worth having them all looked at.
Water reaches the downspout and comes out the bottom, no drips. The run is tight. If it "leaks" in a storm, it's overflow. Move on to step three.
Water pools in the middle and takes a long time to reach the downspout. The pitch is off. Sight down the run and you'll see the dip. That's a re-hang, and it explains why the gutter overflows in the middle in heavy rain.
Water disappears into the gutter but nothing comes out the downspout. The downspout is plugged, almost always at the top elbow. Flush it from the top; if that doesn't clear it, the elbow comes apart.
Water drips from the back of the gutter, between it and the fascia. Either the gutter is hung too low and water is going over the back lip, or there's no drip edge and the hose water is running along the fascia. Either way, this one goes to step four.
Step three: overflow
If the run is tight but overflows in rain, the gutter isn't leaking — it can't take the water fast enough. The usual reasons here are a 2x3 downspout on a run that carries a big roof, one downspout on a 50-foot run, or a 5-inch gutter under a two-story roof plane in a two-inch-an-hour storm. Why gutters overflow in San Antonio rain sorts those out by where the water comes over. Resealing an overflowing gutter fixes nothing, so it helps to know this before someone sells you a reseal.
Step four: water behind the gutter
This one fools people. If the fascia is stained and the gutter is dry, water is getting behind the gutter from above. Look at the roof edge: is there a metal drip edge under the first row of shingles, bent down into the gutter? Do the shingles extend past the fascia by about half an inch to an inch? On a lot of San Antonio roofs replaced after a hail year, especially the 1970s ranches in Leon Valley and the older parts of Universal City, there's no drip edge and the shingles stop short. Rain runs down the fascia behind the gutter, rots the board, and the hangers let go. It's a roofing detail, and a gutter crew should tell you so rather than reseal a gutter that isn't leaking.
The two-story version
No ladder. Wait for a rain, or run the hose up onto the roof from a window if you can do it safely, and watch from the ground: where does water come over, drip, or streak? Photograph it. The pattern — corner drip versus mid-run overflow versus fascia streak — tells a contractor most of what they need before they arrive.
What to tell a contractor
"Corner leak on the front left, downspout on the back trickles, fascia stained on the west side." That's a call a contractor can price fairly closely over the phone. Corner reseals and downspout fixes are on the gutter repair page; if the hose test turned up a run that's tight but overflows on every side, the honest conversation is about sizing, and it starts on the installation page. Gutter leak repair San Antonio homeowners book after a hose test tends to be one visit. The ones booked from "it leaks somewhere" tend to be two.
Safety before you start
Set the ladder on firm, level ground and never rest it on the gutter itself; a standoff keeps it off the trough. Keep your hips between the rails and move the ladder rather than reaching. Wear gloves, because old gutter edges and screws are sharp. Skip the ladder entirely on a two-story house, on a tile or metal roof edge, or if you're not comfortable. The ground-only version of the test still tells you most of what you need.
Stopgaps until the repair
- A corner that drips onto a step or the AC pad: set a splash block or a bucket under it so the water isn't soaking one spot.
- A downspout that has come apart at the elbow: push it back together and fix it with a short sheet-metal screw until it can be replaced properly.
- A run that has pulled away at one end: a loop of wire to the nearest sound hanger can stop it swinging in the wind.
None of these are repairs. They keep water off the fascia and the slab until the job can be done right.
Common mistakes
Running the hose at full blast, which overflows a tight gutter and makes it look like a leak. Testing a whole run at once instead of one section at a time. Smearing new caulk over old cracked sealant, which peels in the first summer. And assuming the drip is from the gutter when the stain is on the fascia behind it.
Common questions
Can I reseal a leaking gutter corner myself?
On a single-story house, yes, if you scrape the joint back to bare metal, clean it, and use a gutter sealant rather than general-purpose caulk. A bead over the old sealant won't hold.
Why does my gutter only seem to leak in heavy rain?
Usually because it isn't leaking; it's overflowing, or water is running behind it at the roof edge. A real joint leak drips in a light rain too, and the hose test at moderate flow is how you find a gutter leak and tell the two apart.
Does a small gutter leak need fixing right away?
Soon, if it drips onto the fascia, a doorstep or the slab. A slow corner drip soaks the same board every time it rains, and the board is what holds the gutter up. A drip that lands harmlessly on a lawn can wait for a dry week, but not for years.
Need gutter work in San Antonio?
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