Clean exterior drains by locating and removing the obstacles preventing the drain from functioning properly. The most common problem with exterior drains is blockages caused by an excessive buildup of debris or a damaged drainage system.
Because exterior drains process rainwater, dirt or debris is likely to fall into the system. Roots or above-ground pressure can cause pipe damage that results in a stoppage. Water often pools at the area in or around the drainage system where damage or a blockage is present.
Clear any visible blockage from the downspouts or other similar plumbing that leads to or from an exterior drain. If the problem persists, locate the obstacle within the pipe.
Try flushing the obstacle loose with a high-pressure water hose or removing the clog with a plumbing snake that employs a claw at the end of a retractable cord to grab at debris within a pipe. If neither of these methods yields results, use a metal plumbing snake to locate the clog by extending the tool into the pipe until it stops at the clog. By measuring the spent cord, you can estimate the location of the clog. Use a metal detector to find the end of the snake while it is still in the pipe. After locating the stoppage, dig up the pipe and remove the clog, or repair the pipe before reburying the drainage pipe.