How to Repair a Gutter Downspout Elbow: Step-by-Step Guide

Frequently Asked Questions

How do I know if my downspout elbow needs to be replaced?

Signs that a downspout elbow needs replacement: water drips or streams from the elbow joint during rain rather than flowing through the downspout, the elbow is visibly cracked or split, the elbow has separated from the downspout tube and hangs loose, or the elbow is bent out of alignment so water misses the next section. A small drip at the joint seam may be fixed with sealant; a cracked or separated elbow requires full replacement.

What is the difference between an A-elbow and a B-elbow?

On a standard downspout, the top elbow (called an A-elbow or offset elbow) redirects the downspout from the gutterline out away from the wall so the vertical run clears any window trim or siding features. The bottom elbow (B-elbow) redirects the vertical run at the bottom to angle water away from the foundation. Both elbows are the same physical part — A and B just refer to their position and how they are oriented on the downspout.

What size downspout elbow do I need?

Match the elbow to your existing downspout dimensions. The two most common residential sizes are 2x3 inch (for 2x3 rectangular downspouts, the most common on older homes) and 3x4 inch (wider, more common on newer homes and homes with larger gutters). Round downspouts use 3-inch or 4-inch round elbows. Measure the outside dimensions of your existing downspout before buying — a 2x3 elbow will not fit a 3x4 downspout.

Do I need sheet metal screws to secure a downspout elbow?

Yes, for a permanent repair. Downspout sections and elbows are friction-fitted together (one end crimped slightly smaller to slide inside the other), but that friction alone is not enough to hold against wind and water weight. Drive one or two 1/4-inch hex-head sheet metal screws through each joint — they pull the joint tight and prevent the sections from separating. Pre-drill if the metal is thick. Use aluminum or stainless screws to prevent rust streaks.

Can I seal a leaking downspout elbow joint instead of replacing it?

Yes, for minor seam leaks. Clean and dry the joint area thoroughly, then apply gutter and flashing sealant (not standard silicone or caulk) to the inside of the joint. For exterior application, butyl rubber gutter sealant bonds well to aluminum and stays flexible through temperature cycles. If the elbow is cracked through or has a hole, replacement is more reliable than patching.

How do I prevent downspout elbows from separating again?

Secure every joint with sheet metal screws — two per joint is sufficient for most applications. For elbows that separate repeatedly due to ground freeze-thaw movement at the bottom of the downspout, add a concrete downspout splash block or a flexible downspout extension to reduce the physical stress on the bottom elbow. Keeping the downspout free of debris reduces the weight load that strains joints during heavy rainfall.

Replacing a gutter downspout elbow: (1) Identify the elbow type: A-style (front-to-back swing, most common) or B-style (side-to-side). Bring the old elbow to the hardware store or measure the downspout width (2x3 or 3x4 inch) for the correct replacement.

A leaking or separated downspout elbow sends water where you do not want it — against your foundation, behind your siding, or into a crawl space. Replacing an elbow takes about 20 minutes and costs under $10.

What You Need

• Replacement downspout elbow (2x3 or 3x4 inch, match your existing downspout)
• Sheet metal screws 1/4 inch hex head — for securing all joints
• Gutter sealant butyl rubber — for sealing the joint seam after screwing
• Drill with hex bit
• Tin snips (if cutting the new elbow to fit)
• Ladder

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Step 1: Diagnose the Problem

Get on a ladder and inspect the elbow during or after rainfall to identify exactly where the water is escaping:

• Drip at the joint seam: The seal between the elbow and the downspout tube has failed. Try sealant first before replacing.
• Crack or hole in the elbow body: Replace the elbow — patching aluminum cracks is a temporary fix at best.
• Separated joint: The elbow has pulled away from the downspout section above or below it. Reseat and screw the joint, or replace if the crimp is damaged.
• Elbow angled away from the wall or visibly bent: Replace the elbow and check the downspout hanger above it.

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Step 2: Remove the Old Elbow

Downspout elbows are connected by having one crimped (smaller) end slide inside the adjacent downspout section. The sections are typically held together by sheet metal screws driven through the overlap.

1. Locate and remove any sheet metal screws at both connections — top and bottom — of the elbow you are replacing. A drill with a hex bit backs them out quickly.
2. Twist the elbow slightly while pulling it away from the joint. If it is stuck from years of paint or oxidation, wiggle it gently or use a flat pry bar with light pressure.
3. If the elbow connects to the gutterline at the top, also disconnect the downspout outlet from the gutter (the small outlet fitting that pokes through the gutter floor). You may need to remove one or two screws there as well.

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Step 3: Buy the Correct Replacement Elbow

Bring the old elbow to the hardware store or measure it before ordering:

• Outside dimensions of the downspout tube: 2x3 inch is the most common on homes built before 2000; 3x4 inch is standard on newer construction and homes with larger 6-inch gutters.
• Elbow angle: Standard elbows are 75-degree offset (labeled A-elbow). Bottom discharge elbows are typically 45 or 90 degrees — match the angle of your existing elbow by measuring it or bringing it in.
• Material: Match aluminum to aluminum. If your downspouts are white or brown painted aluminum, buy a pre-painted elbow in the matching color.

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Step 4: Install the New Elbow

Downspout sections are designed so the upper section’s crimped end slides inside the lower section — this ensures water flows into the lower section rather than between them. Follow this same convention when installing the elbow.

At the top connection (elbow to gutter outlet or upper downspout):

1. Slide the upper downspout section’s crimped end into the top opening of the new elbow.
2. Align the elbow so the lower outlet is angled parallel to the wall (for a mid-run elbow) or angled away from the foundation (for a bottom elbow).
3. Drive two sheet metal screws through the overlap on opposing sides of the joint.

At the bottom connection (elbow to lower downspout section):

1. Slide the crimped (upper/smaller) end of the elbow into the top of the lower downspout section.
2. Confirm the alignment — the lower section should hang plumb or close to plumb against the wall.
3. Drive two sheet metal screws through the joint.

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Step 5: Seal the Joints

After screwing the joints, apply a bead of gutter sealant on the inside of each joint — run the sealant around the full perimeter where the two sections overlap. This waterproofs the connection even if the crimped fit is not perfectly tight.

Do not apply sealant to the outside of the joint only — exterior sealant peels over time. The internal bead is protected from UV and mechanical wear.

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Step 6: Reattach the Downspout Hanger

If you removed a downspout hanger (strap bracket) during disassembly, reinstall it now. Downspout hangers should be spaced no more than 6 feet apart along the vertical run to keep the downspout from pulling away from the wall. Drive the hanger screw or nail into the wall framing, not just the siding — use a 2-inch or longer exterior screw to reach the sheathing or stud behind the siding.

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Step 7: Test with a Hose

Run a garden hose into the gutter above the repair and observe the elbow joints. Water should flow smoothly through the elbow with no drips at the seams or the screw holes. If you see a slow drip at a screw hole, back the screw out, apply a small dab of sealant to the threads, and re-drive.

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Related Guides

• How to Fix a Sagging Gutter
• How to Fix a Clogged Downspout
• How to Fix Leaking Gutters