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Almost every gutter problem is one problem

We've now written more than fifty guides about gutters. Somewhere in the middle of that, a pattern became impossible to ignore: the symptoms homeowners describe are almost all the same fact, reported six different ways. That fact is standing water — and once you see it, the whole subject collapses into something simple.

Six symptoms, one cause

What you notice	What's actually happening
"My gutters smell"	Debris rotting in water that never drained. →
"Mosquitoes, and I have no pond"	The trough is the pond. Nobody empties it.
"Pinholes / corrosion"	Wet sludge held against aluminum for months.
"The downspout froze"	It was holding water. A draining spout has nothing to freeze. →
"It's sagging"	Water is heavy. ~1.5 gal/ft, ~8.3 lb/gal. →
"Ice dam every February"	Standing water freezes first — that plug is the anchor. →

Six service calls. Six diagnoses. One gutter that doesn't drain.

Why it compounds

Standing water isn't a symptom that sits still — it's a loop that tightens.

Water sits in a low spot. Water is heavy, so it pulls on the hangers there. The hangers give slightly, so the low spot gets lower. A lower spot holds more water. More water pulls harder. Meanwhile debris collects in the puddle (dry debris blows out; wet debris stays), which holds more water still, and rots, and corrodes the metal underneath it.

That's why gutters seem to work fine for a decade and then fail all at once. They didn't. The loop had been running the whole time — you just noticed at the point where it produced a smell, or an ice dam, or a section on your lawn.

The one-minute test

Run a hose into the high end of the run. Shut it off. Wait one minute.

Empty trough? Your gutters drain. Whatever's bothering you is something else — and there are only a few candidates: a missing drip edge (water behind), a valley (water over one corner), or genuine capacity (overflow only in downpours).

Water still sitting? You've found it. That's the cause of the smell, the mosquitoes, the corrosion, the sag, and the February ice. Not six problems. One.

Why it's sitting — three answers

Pitch. Gutters need ~¼ inch of fall per 10 feet. Too flat and water stands after every rain. Fix: re-pitch, $200–$500. →

A failed hanger. One loose hanger makes one dip. That's why the smell is often in one specific stretch. Fix: re-hang, $200–$500. →

A blocked downspout. The trough looks half-decent while the outlet is plugged and everything upstream is a pond. Fix: flush it. →

Note the prices. The cause costs a few hundred dollars. The consequences — fascia rot at $15–$30/ft, ice-dam water damage inside the house, a replacement you didn't need — run into thousands. That asymmetry is the entire argument for looking.

What this reframes

Cleaning isn't about tidiness. It's about drainage. A gutter with leaves that still drains is doing its job; a spotless gutter holding an inch of water is not. That's why flushing the downspouts matters more than scooping the trough — and why a 20-minute "cleaning" that skips them accomplished nothing.

Guards aren't magic. They keep the trough clear so water keeps moving. That's the mechanism — not a force field. It's also why guards help with ice dams (less standing water to freeze) but don't prevent them (the attic is still warm). →

"Fix the gutters" is often wrong. If water sits because the pitch is off, replacing the gutters with new ones at the same wrong pitch buys you the same problem in nicer aluminum. Ask what's causing the water to sit. →

The whole system in one sentence

Water must arrive in the trough (drip edge), move along it (pitch and hangers), leave through the downspout (enough of them, big enough), and land far from the house (4–6 feet, 10 on clay). Four stages. Every gutter problem is a failure at one of them, and standing water is what three of the four look like.

What to do with this

Next time something is wrong with your gutters, don't start with "what do I replace." Start with: is water sitting, and why? One minute with a hose answers it. It's the cheapest diagnostic your house offers, it turns six confusing symptoms into one specific question, and it's the difference between a $250 fix and a $2,800 quote.

Get a pro who diagnoses before quoting →

FAQ

What causes most gutter problems?

Standing water. A gutter that drains completely does not smell, does not breed mosquitoes, does not corrode from the inside, does not freeze, does not sag under weight, and does not anchor an ice dam. Almost every symptom homeowners describe is water sitting where it should be moving.

Why does standing water damage gutters?

It attacks from four directions at once: it holds moisture against the aluminum and corrodes it from the inside, its weight loosens hangers and worsens the pitch, it decomposes debris into odour and mosquito habitat, and it freezes first in winter to become an ice dam anchor.

How do I know if my gutters hold standing water?

Run a hose into the run, shut it off, and wait one minute. The trough should be essentially empty. Water still sitting means the pitch is wrong, a hanger has failed, or the downspout is blocked — and it is the cause of whatever else you are noticing.

Why do gutters hold water?

Three reasons: incorrect pitch (they need about a quarter inch of fall per ten feet), a failed hanger creating a low spot, or a blocked downspout backing water up. All three are cheap to fix compared with what standing water eventually costs.