How to Find a Gutter Leak Before You Call Anyone
Half the "gutter leaks" we're called to 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 us most of what we need before we get there.
What to tell us
"Corner leak on the front left, downspout on the back trickles, fascia stained on the west side." That's a call we can price close to exactly 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.
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