Outdoor drains collect general runoff and direct it away from your home's foundation or your garden, and when one gets clogged with leaves or silt, locating the actual clog isn't always straightforward. This is particularly true for French drains, which are sometimes little more than trenches filled with gravel. If the drain has a pipe, you can use water pressure, an auger or even a stick to clear it, but if silt has clogged a gravel-filled trench, you may have to dig up the drain to clear it.
You may have a storm drain on your patio or on the driveway; it consists of a grate installed in a depression on the concrete, and it's connected to a pipe that directs water to a safe place, such as a catchment basin or simply to a downward slope along which the water can drain away. When leaves or debris form a clog, the clog may be near the grate, but not always. Sometimes, the clog is closer to the outlet, and that can be far away.
Clearing a Storm Drain
Lift the grate, put on a pair of gloves and pull out whatever debris you can reach with your hands. Use a stick to reach deeper if some debris is out of your reach. This may be all you need to do -- check by shooting water into the drain with a garden hose.
Screw a bladder-type drain cleaner onto your hose to dislodge deeper obstructions. The rubber bladder on this tool expands when you turn on the water to fill the drain pipe, and the small aperture on the end creates a powerful jet of water. The bladder prevents back flow, and the water pressure eventually becomes large enough to move stuck leaves, sticks and other organic matter. It won't clear a clog caused by concrete, rocks or other sediment, though.
Locate a sediment clog by using a plumbing auger. Feed the auger into the drain until it hits the obstruction, then use a metal detector to find the end. Dig down at that point, using a shovel, cut into the pipe, remove the clog, repair the pipe and backfill.
French drains are typically little more than gravel-filled trenches that rely on gravity to drain water. Water that flows into the trench follows the slope of the trench. Some French drains are reinforced with perforated drain pipe, and if this pipe clogs, it's usually because one end is open and leaves have gotten into it. You may be able to clear this type of clog with an auger or a jet of water, but because the pipe is perforated, a bladder-type drain cleaner won't work.
If your clogged French drain is clogged, and water is collecting around your foundation or it's creating pools in your garden, there's little else to do but dig the trench out and redo the drain. To prevent clogging in the future, bury perforated pipe in the bottom of the trench and cover it with a fabric filter.