A French drain is a perforated drainage pipe that can help channel groundwater out of an area. These drains are relatively low-maintenance, but they do need to be cleaned out about once a year because dirt and other debris can get into the drain through the holes designed to allow water to flow into the drain. It is best to clean out your French drain on a regular schedule so that you can prevent a clog from occurring. However, if you have postponed the cleaning for too long, then you might have a larger job on your hands.
Wear your garden gloves. You are going to be getting dirty, and there is a chance you might have to pull some debris out of the drain at some point. The gloves will protect your hands from sharp pieces of debris and also any little critters that might be living in or around your drain.
Locate the beginning of your French drain. If it is outside, then it will generally be at the top of the grade. It might be covered by weeds or grass, and dirt might have fallen into the hole. This will not necessarily have affected how the drain works because the holes in the drain will allow water to seep in throughout the length of the drain.
Use the garden hose to send a steady stream of water down the French drain. Do not start out with the pressure cleaner because if the drain has a major clog, you will just end up with lots of water firing back in your face. Note whether the water is backing up, or whether it appears to be flowing freely. If it is backing up, then you can be prepared for a clog.
Clean out the French drain using the pressure cleaner. If you suspect a clog, be very careful to stand to the side when you fire the water down the drain. Try to angle the stream of water to hit first the bottom of the length of the drain, then the sides. If the water continues to back up, you need to move on to the sewer snake.
Use the sewer snake to dislodge the clog. A sewer snake is a long, flexible tube. You can feed it into the mouth of the French drain until it meets resistance at the clog. Use the snake to gently prod the clog and loosen it. Once it feels loose, send a strong stream of water from the pressure cleaner down the tube again. It should knock the clog free. If it does not, reinsert the sewer snake and work on dislodging the clog further and then attack it with more water.
Check the landscaping cloth. If your French drain is outside, it should be covered with a thin layer of landscaping cloth underneath the gravel or dirt that hides the drain. If you have a lot of clogs, you might want to check to see whether the cloth has slipped away from the drain. This type of cloth helps prevent dirt and debris from entering the drain, and if it has slipped, then you might need to replace it with a new piece of cloth. If your drain is inside or if it is part of an elaborate landscaping theme, you might decide to skip this step. If you do experience clogs but are unable to check the cloth, then you need to start cleaning your drain out more frequently.