Diagnostics

Why Your Gutters Are Leaking and How to Diagnose Where

Last updated: May 23, 2026 · Reading time ~5 min

Gutter leaks come from four sources: (1) miter corners (most common — 60% of leaks), (2) end caps, (3) downspout connections, and (4) sealant failure at hangers. Diagnose by running a garden hose at the high end and watching where water first emerges. The leak source is almost always uphill from where you SEE drips.

The hose test

Get on a ladder. Run hose water into the highest end of the gutter run. Watch from the ground as water moves down. Note exactly where water first emerges below the gutter.

Important: drips fall behind the gutter face often, so the LOOK like they're coming from the wall. The source is almost always at a miter or end cap above.

The 4 common leak sources

Miter corners (60%): Old sealant has failed. Visible white residue. Fix: clean, re-seal.

End caps (20%): Same issue — sealant failure at the terminus. Fix: pop off, re-seal.

Downspout drop outlet (15%): Where the downspout drops out of the gutter bottom. Sealant fails here too. Fix: re-seal.

Through-hole leaks (5%): Hail or corrosion punched a hole in the gutter itself. Fix: patch or section replace.

Frequently asked

Can I patch a small hole with caulk?

Short-term yes (1-2 years). Proper fix is a metal patch or section replacement.

Why does the same miter leak every few years?

Sealant has a 7-15 year life. Frequent re-seal at same spot might mean improper original prep (rust under sealant, wrong sealant type).

Will gutter guards fix leaks?

No — guards are for debris, not leaks.

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