Four of the most common problems rain gutters incur are leaking, sagging, overflowing, and pooling runoff around the house. If left unattended, any one of these conditions can cause serious water damage to the house and its foundation. Fortunately, the fixes are within the realm of even a modestly skilled do-it-yourselfer.
How to Fix Leaking Rain Gutters
If your gutters are leaking, the prime suspects are the joints between sections. Standing water in gutters eventually will rust galvanized steel seams or seep through the seams in aluminum gutters.
First check for signs of standing water and sagging. Adjust or add gutter hangers as needed. Allow the insides of the gutters to dry out, brush leaking seams clean, and then apply silicone-rubber caulking compound along the seams on the inside and outside to seal the leaks, as shown below left. Patch small holes with roofing cement. Use a putty knife to spread the cement generously around the hole. Try to do this on a warm day, but, if the weather is cool, warm the cement to room temperature so it spreads easily.
Repair larger holes in gutters by covering them with patches. Take a sheet-metal patch, embed it in roofing cement, and then apply another coat of cement over the patch, as shown below right.
If your region delivers abundant rainfall, you may want to have your downspout run into a dry well. The well should be a hole 2 to 4 feet wide and 3 feet deep, or a 55-gallon drum—with both ends removed and filled with rocks—that you’ve buried and punctured with holes. Underground drainage pipes should slope to the dry well, which will keep water away from the house’s foundation. Check your local building codes before installing.
How to Fix Sagging Rain Gutters
When full of water, rain gutters can become extremely heavy. As a result, the types made of flexible materials such as aluminum, vinyl, and galvanized steel can begin to bend and sag and their hangers loosen. As this happens, they cease to do a good job of draining rainwater efficiently, allowing water to pool along their lengths. This, of course, just exacerbates the problem, making them heavier and causing them to sag even more.
To determine if your rain gutters sag, check for signs of standing water or water marks along the inner sides of the gutters. With a level, check the slope—gutters should drop about 1/4 inch for every 10 feet of run toward the downspouts. 
To fix them, you may need to replace the hangers or, at the very least, reseat them. If the gutters are held by spike-and-ferrule hangers, use a hammer to drive the long spike, making sure it goes into solid wood. If it does not grab securely, you may need to replace it with an even longer galvanized nail or, better yet, a long screw.
To tighten clip-style gutter hangers, you will need to lift the roofing material along the eaves and refasten the hangers to the sheathing. Be careful not to crack or create holes in the roofing.
How to Fix Overflowing Rain Gutters
If your gutters overflow during a heavy rain, either the gutters and/or downspouts are clogged, the gutters are sagging and thereby preventing water from reaching the downspouts, or the gutters and downspouts are not large enough to handle the volume of rain runoff.
In most cases, gutters overflow because leaves and debris are clogging them, essentially creating dams that prevent water from flowing to the outlets above the downspouts. In fact, these clogs often occur right at the outlets. When this is the case, it’s time to clean out the gutters. (For more about this, see How to Clean Rain Gutters.)
Gutters that sag are a different issue—and the more they fill up with water, the more likely they are to sag because they become so heavy when full. If the gutters overflow but are not sagging or clogged, you will probably need to install new, larger downspouts and gutters.
How to Fix Downspouts That Pool Runoff Around the House
Downspouts that dump rainwater right at the base of your exterior walls can create serious problems. As water pools and soaks into the soil, it can eventually work its way into the foundation. For this reason, it is important to direct rainwater away from the house.
The best way to do this is to use a downspout diverter. These simple devices fit onto the bottom of downspouts and—as in the case of the one shown here—unfurl to carry water several feet away from the house. Called an “automatic recoiling downspout,” it is a simple and inexpensive device.
Another option is to bury 4-inch-diameter ABS drainpipe under the ground, but keep in mind that this may be clog up over time.
Raindrain 46" Automatic Recoiling Downspout - Green #URD46GR
