Clogged Downspouts: How to Flush and Clear Them Before Backup

To clear a clogged downspout, start by flushing it from the top with a garden hose. If water still backs up, tap the downspout to locate the blockage, then use a plumber's snake (drain auger) from the bottom to break it apart and flush again. Most clogs sit at the elbow where the downspout meets the gutter or at the lower elbow near the ground, and you can usually clear them in under 30 minutes with basic tools.

This guide walks through the full process — what tools you need, how to find the clog, and how to know when the problem is bigger than a clog.

How do I know my downspout is actually clogged?

Not every gutter problem is a downspout clog. Before you start pulling things apart, check for these signs:

• Water overflows the gutter during rain, even though the gutter itself looks clean.
• You hear water trickling inside the downspout but nothing comes out the bottom.
• Water shoots out the top seam where the downspout meets the gutter outlet.
• The downspout sounds hollow and dull when you tap it, except for one section that sounds packed.
• Standing water sits in the gutter 24+ hours after rain stops.

If water flows freely from the bottom of the downspout during rain but the gutters still overflow, your problem is probably in the gutter itself (debris buildup or a slope issue), not the downspout.

What tools do I need to unclog a downspout?

For most clogs, you only need basic homeowner tools:

• Garden hose with a spray nozzle (essential)
• Sturdy ladder — extension ladder for two-story homes
• Work gloves — wet leaf debris carries bacteria and the occasional wasp
• Plumber's snake / drain auger — a 15- to 25-foot manual auger runs about $15–35 at hardware stores
• Bucket or tarp to catch debris at the bottom

For tougher clogs, optional add-ons:

• Pressure washer with a low-pressure tip (1500–2000 PSI is plenty)
• Downspout flushing attachment for your hose — about $10–25
• Leaf blower for dry, lightweight clogs at the top of the downspout

Step-by-step: flushing a clogged downspout

Step 1: Clear the gutter first

If the gutter above the downspout is full of leaves, scoop those out by hand before doing anything else. Otherwise, you'll just wash that debris down into the clog and make it worse. Bag the debris — don't toss it in the lawn where it'll wash back into the gutter next storm.

Step 2: Flush from the top with a hose

Run your hose up the ladder, stick the nozzle into the downspout opening at the gutter, and turn it on full blast. Three things can happen:

1. Water flows out the bottom freely. No clog — you're done.
2. Water backs up into the gutter immediately. Hard clog near the top, usually at the elbow.
3. Water drains slowly or trickles out the bottom. Partial clog somewhere in the middle or at the bottom elbow.

Step 3: Locate the clog

Tap the downspout from top to bottom with the handle of a screwdriver or your knuckles. A clear section sounds hollow. The clog sounds dull, packed, or solid. Most clogs sit in one of two spots: the upper elbow (where the downspout turns away from the roofline) or the lower elbow (the curved piece near the ground that directs water away from the foundation).

Step 4: Snake it from the bottom

Feed a plumber's snake up from the bottom opening of the downspout. Crank slowly. When you hit resistance, work the auger back and forth to break up the debris. Pull the snake out and you'll usually drag wet leaves, shingle grit, and sometimes a bird's nest with it.

If the snake won't go up from the bottom, try feeding it down from the top. Some downspouts have multiple elbows that make snaking from one direction impossible.

Step 5: Flush again

Run the hose from the top one more time. Water should now flow steadily from the bottom. If it does, you're done. Reattach any sections you disconnected and check that all seams and elbows are sealed.

What if the clog won't budge?

If snaking and flushing don't work, the downspout may need to come apart. Most aluminum downspouts are held together with sheet metal screws and crimped elbows. Disassembly is straightforward:

1. Remove the screws holding the downspout to its straps on the wall.
2. Twist and pull the elbows apart — they're friction-fit with a few screws.
3. Lay the section on the ground and clean it out with a hose or by hand.
4. Reassemble in reverse order, re-screwing each joint.

Be careful with older downspouts. Aluminum gets brittle after 15–20 years in the sun, and the seams can crack if you torque them too hard. If you snap a section, replacement downspout pieces run about $8–15 per 10-foot section for standard 2x3 or 3x4 aluminum, plus another $3–8 per elbow.

Can I use a pressure washer on a downspout?

Yes, but carefully. A pressure washer with a 25- or 40-degree tip at 1500–2000 PSI will blow out most clogs in seconds. Higher pressure can dent or split aluminum downspouts, especially older ones.

Direct the wand up from the bottom opening or down from the top. Stand to the side, not directly underneath — the debris that flies out is usually wet, smelly, and full of grit. Wear safety glasses.

Never aim a pressure washer at gutter seams, end caps, or hangers. The water can force itself behind sealants and create leaks where there weren't any before.

What causes downspouts to clog in the first place?

Knowing the cause helps you prevent the next clog. The most common culprits:

Cause	Where it clogs	Prevention
Leaves and twigs	Upper elbow	Gutter guards or twice-yearly cleaning
Shingle grit (granules)	Lower elbow, underground drain	Replace aging roofs; rinse gutters annually
Bird and rodent nests	Top of downspout	Wire mesh outlet strainers
Tennis balls, toys	Anywhere	Outlet strainers
Ice (winter)	Entire downspout	Heated cables; proper attic insulation

Homes surrounded by mature trees — especially oak, maple, and pine — tend to clog two to three times per year. Homes with no overhanging trees may go years between clogs.

When should you call a pro instead?

Call a gutter contractor or cleaning service if any of these apply:

• You have a two- or three-story home and aren't comfortable on a tall extension ladder. Falls from ladders send tens of thousands of Americans to emergency rooms each year, according to the CDC.
• The downspout drains into an underground pipe and the clog is below ground. Underground drain lines need a longer power auger or a hydro-jetting tool that most homeowners don't own.
• You've cleared the clog twice in one season. Something else is wrong — bad slope, undersized downspouts, or a damaged outlet.
• The downspout is damaged, separated, or pulling away from the wall. You need repair, not just cleaning.

Standard gutter and downspout cleaning runs about $120–250 for a typical single-story home, and $200–425 for a two-story. Underground drain clearing with a power auger or hydro-jet usually costs $200–600 depending on length and access. These ranges are approximate and vary by region.

How do I keep downspouts from clogging again?

A few low-cost upgrades pay for themselves quickly:

• Outlet strainers (wire mesh "bulbs") drop into the downspout opening at the gutter and catch leaves before they enter. About $3–8 each.
• Gutter guards reduce — but don't eliminate — debris in the gutter itself. Installed cost runs about $7–12 per linear foot for mesh and reverse-curve styles.
• Twice-yearly cleaning in late spring and late fall handles most debris cycles in tree-heavy yards.
• Splash blocks or downspout extensions keep the discharge area clear and prevent backflow during heavy rain.

For more on prevention, see our guides in the maintenance section or browse the glossary for terms like "outlet," "elbow," and "downspout extension."

The bottom line

Most clogged downspouts can be cleared in under an hour with a hose, a ladder, and a $20 plumber's snake. Start at the top with water, locate the clog by tapping, and snake from the bottom up. If you've tried twice and the clog won't move, or if the downspout drains into an underground pipe, it's worth bringing in a pro before the next storm sends water back into your foundation.

Need help finding someone reliable? Get matched with a local contractor using the form on our home page.

What does ignoring a clogged downspout actually cost?

Far more than a 30-minute flush. When a downspout backs up, water overflows the gutter and runs down the fascia, into the soffit, or against the foundation—and water damage is one of the most common and expensive home claims. The Insurance Information Institute reports that water damage and freezing rank among the top causes of homeowners insurance claims, affecting about one in 60 insured homes every year. Clearing a clog today prevents the chain that leads there:

• Overflow → saturated fascia and soffit rot ($6–$30 per linear foot to repair).
• Foundation pooling → basement seepage and settling.
• Winter freeze → an ice plug that can bend or detach the downspout.

The math is lopsided: a $0 hose flush versus four-figure water-damage repairs. Clearing downspouts before the rainy season is the cheapest insurance you’ll buy all year.