How to unclog a downspout (above ground and underground)

Gloved hand holding a downspout elbow packed with wet leaves and maple keys beside a brick house

To unclog a downspout, find the blockage first: it is almost always at the gutter outlet or a bottom elbow. Clear the outlet by hand, then flush from the top with a garden hose. If water still backs up, remove the bottom elbow and push the clog out. Underground sections need a drain snake or a plumber.

How can you tell the downspout is the clog?

A clogged downspout has a signature a clogged gutter does not. The eavestrough overflows hardest right beside the outlet instead of along the whole run, and the bottom of the spout stays dry or dribbles while rain is pouring off the roof. On a clear day you can confirm it without climbing anything.

Overflow concentrated at one corner, directly above the downspout
A silent or dribbling spout during a downpour, sometimes with a gurgle as air fights the blockage
The tap test: rap the downspout with a knuckle or a screwdriver handle from the bottom up. Clear sections ring hollow; a packed section sounds dull and flat
A dent, bulge or split seam where debris and ice have been pressing from inside

If the water spills along the whole length of the gutter instead, the trough itself is full (see the five signs your gutters are clogged) or the run has lost its slope.

Where do downspout clogs actually form?

Water moves fast in a straight pipe, so debris rarely stops mid-run. It stops where the path narrows or turns: at the outlet hole in the gutter floor, and at the elbows, meaning the gooseneck under the eave and the kick-out at the bottom. On GTA streets the usual plug is a wad of wet maple leaves or maple keys packed hard with shingle grit.

Where	What it usually is	How it comes out
Gutter outlet	Leaves matted over the hole like a sink plug	Lift it out by hand from the ladder, then flush
Top elbow (gooseneck)	Debris wedged at the first bend under the eave	Flush from the top; unscrew the elbow if it will not budge
Straight section	Rare: a nest, a ball, or a crushed length	Tap test to find it; push through from below
Bottom elbow	Compacted grit and keys at the last turn	Remove the elbow or extension, clear it, refit
Underground pipe	Roots, silt, or a collapsed section	Drain snake or camera inspection by a drain contractor

How do you clear a clogged downspout safely?

Pick a dry day and start at the bottom, where there is no ladder involved. Most clogs clear without special tools; the only real risk in this job is the climb.

1Start on the ground. Pull off the extension and the bottom elbow (most are held by two to four short screws, or are simply friction-fit) and clear whatever is packed inside.
2Flush from below. Push a garden hose up the spout as far as it goes and turn it on full. The water loosens debris and carries it back down and out.
3If the outlet is still blocked, go up. Set an extension ladder on firm, level ground at the 4-to-1 angle, one foot out for every four feet up, and use a standoff so it never rests on the gutter.
4Clear the outlet with a gloved hand, lifting debris away from the hole rather than pushing it down the spout.
5Flush from the top with the hose at full flow and watch the bottom. A steady, full-bore stream at the discharge means the path is clear; a trickle means something is still in there.
6For a stubborn plug, feed a hand-crank drain snake up from the bottom, gently. Aluminum spouts dent and split if you force them.
7Refit the elbow with short screws (long ones poke inside and snag the next load of leaves), reattach the extension, and aim it 1.5 to 2 metres away onto ground that slopes away from the house.

What if your downspout goes underground?

Many older GTA homes have downspouts that disappear into a pipe at ground level. That pipe might lead to a storm connection, a dry well, an outlet at the back of the lot, or a cracked clay line that now leaks beside the footing. Before you snake anything, find out which one you have.

The quickest test: separate the downspout from the pipe at grade and run the hose down the spout on its own. If the spout runs free, the blockage is underground. Clearing a buried line is drain work: a drain contractor can snake it and run a camera to see whether it is silt, roots or a collapse. In Toronto, downspouts must be disconnected from the City's sewer system unless the City has granted an exemption, so check what the bylaw asks of homeowners before reconnecting anything.

Where local rules allow it, the simplest permanent fix is often to stop sending roof water underground at all and redirect it above ground with an extension. Where that water lands matters as much as the clog did.

How do you keep downspouts from clogging again?

Clean the gutters on the GTA's real calendar: late spring after the maple keys, late fall after the leaf drop. The timing guide has the windows.
Look at the outlets after a big wind. One gusty October evening can deliver a season of leaves to a single corner.
On heavily treed roofs, a 3-by-4-inch downspout has twice the opening of the standard 2-by-3 and clogs far less often. More on sizing.
Outlet strainers stop leaves entering the spout but become the clog if nobody empties them. They only help if someone checks them.
Trim branches that hang directly over the outlet corner.

When should you hand it to a crew?

If the outlet is on the second or third storey, if the clog is packed solid, or if the same spout blocks every season, it is worth having it done properly. Every Gutter Gang cleaning includes a downspout flush and flow test, and a blocked spout gets cleared before the job is called done. In 2026 a full cleaning runs $299 to $499 before HST depending on home type and storeys, and downspout service in Mississauga comes with the same before and after photos as everywhere else.

Frequently asked questions

Can I use a leaf blower to clear a downspout?

Sometimes, on a loose, dry clog: blowing up from the bottom elbow can dislodge leaves. It will not move a wet, compacted plug, and blowing down from the top usually packs debris tighter at the next bend. A garden hose does the same job with better control.

How do I know if my underground downspout pipe is blocked?

Separate the downspout at ground level and run a hose down the spout. If it flows freely on its own but backs up when reconnected, the buried pipe is the problem. A drain contractor can snake it and run a camera to show what is inside.

How often should downspouts be flushed?

Every time the gutters are cleaned, which for most GTA homes is twice a year, in late spring and late fall. A flush proves water actually leaves the system; a gutter that looks empty can still drain into a blocked spout.

Is it normal for a downspout to gurgle?

A little gurgling in heavy rain is just air moving with the water. Loud, constant gurgling combined with overflow at the gutter above usually means a partial clog at an elbow.

Keep reading