How to Unclog a Downspout

A clogged downspout is one of the most common gutter problems, and one of the most fixable without special tools. The whole job comes down to two things: figuring out where the blockage sits, and clearing it without knocking the pipe apart. Work patiently from both ends, use a hose and a snake rather than brute force, and most clogs come loose in a few minutes.

First, confirm it is actually the downspout

Before you start, make sure the downspout is the problem and not the gutter feeding it. If water overflows the gutter along its length, the trouble may be upstream — the gutter itself is full, or overflowing in heavy rain. If water backs up specifically at the outlet where the gutter meets the downspout, or the downspout stays dry during rain while the gutter brims, the clog is in the pipe. Our guide to why a downspout is not draining covers how to tell these apart.

Step 1: Locate the blockage by tapping

You do not need to guess. Walk your knuckles or the handle of a screwdriver down the length of the downspout, tapping every foot or so.

• A clear section sounds hollow and light.
• A packed section sounds dull, flat and solid.

Start at the top and work down. The point where the sound goes from hollow to dull is roughly the top of the clog. That tells you which direction to work from: a clog high up near the top offset is best reached from above, while one low down near the bottom elbow is easier to clear from the ground.

Step 2: Flush from the top with a hose

For many clogs, plain water flow is enough. Feed a garden hose into the top of the downspout — from the gutter outlet if you can safely reach it — and turn it on at a normal, steady flow. The column of water often loosens a soft mass of leaves and washes it down and out the bottom.

Keep an eye on the bottom of the pipe. If water and debris start flowing out, you are winning. If water instead backs up out the top, the clog is holding; shut off before it overflows and move to the snake.

Step 3: Snake a stubborn clog

When water alone will not move it, a plumber’s drain snake (a hand auger) is the right tool. Feed the flexible cable into the pipe from whichever end is closer to the blockage, turning gently as you go. The cable either pushes the packed material through or hooks it so you can pull it back out. Follow up with the hose to flush whatever broke loose.

Go slowly at bends. The snake has to work around each elbow, and forcing it can pop a joint or scratch the inside of the pipe.

Step 4: Open a joint if you have to

Sometimes the fastest route is to take the pipe apart right at the clog — most often at an elbow, where debris tends to pack in. Friction-fit sections usually pull apart with a firm, steady tug. Clear the exposed section by hand or with the hose, then reassemble with the upper piece nested inside the lower one so water stays captured at the seam.

Buried lines are a different job

If the downspout ties into a buried drain line, you cannot tap along it or take it apart. Your options depend on whether the line has cleanouts — capped access points installed along the run.

• With cleanouts: open the nearest one upstream of the blockage and snake toward the clog from there. This is exactly what they are for.
• Without cleanouts: you are limited to working from the downspout inlet or the outlet end, feeding a snake blindly along the buried pipe. It is slower and less certain, which is the whole argument for adding cleanouts when a line goes in.

Methods at a glance

The table below is a rough guide to matching the method to the clog. Results vary with the pipe and the blockage.

Method	Best for	Watch out for
Tapping to locate	Any clog, as the first step	Reading the sound change carefully
Garden hose flush	Soft leaf clogs	Backing up and overflowing the top
Plumber’s snake	Packed or stubborn clogs	Forcing it through elbows
Opening a joint	Clogs at an accessible elbow	Cracking a cold, brittle pipe
Cleanout access	Buried-line clogs	Only works if cleanouts exist

Common mistakes

• Blasting it with high pressure. A pressure washer or a jammed-on hose can separate friction-fit joints and force water out behind the pipe instead of through the clog.
• Forcing a frozen line. Ice will not move, and the pressure can split the pipe or a joint. Wait for a thaw and fix the freezing cause instead.
• Snaking without locating first. Feeding a cable in blind wastes effort; tap to find the clog so you work from the closer end.
• Reassembling joints upside down. Nesting the upper piece outside the lower one sends water down the outside of the pipe at every seam.
• Overreaching on a ladder. The top of the downspout tempts you to stretch. Reposition the ladder or get help rather than leaning out.
• Clearing the same spot forever. Repeat clogs at one elbow point to an upstream cause — dirty gutters or a missing strainer — not a pipe that just needs re-clearing.

The bottom line

Unclogging a downspout is mostly about patience and the right amount of force. Tap to find where the blockage sits, flush with a garden hose, and bring in a plumber’s snake when water alone will not do it — all without the high pressure that separates joints and creates new leaks. If the pipe runs underground, cleanouts turn a frustrating blind job into a quick one, which is why they are worth having. And if the same spot keeps clogging, stop treating the symptom and look upstream at the gutters and the turns feeding it.