What causes catch basins to clog?

MMH Expert_Matt T EXPERT April 24, 2008

Catch basins may be in the yard or at the bottom of driveways that slope toward the home. Catch basins may also be found at low areas around basement walkouts. Clogged catch basins are common.

Common causes include

• clogged or undersized outlet pipes
• basins filled with debris
• basin covers obstructed with debris

Pipes leading from catch basins are susceptible to clogging. Outlet pipes are usually not just a hole in the side of the catch basin. If this were the case, water rising up to the exit pipe would flow out through the pipe, carrying all the floating debris that is at the surface of the water. This includes leaves, twigs, pieces of paper, etc.

A better design is to have the pipe come into the catch basin and turn down. With this configuration, water will only get into the pipe through the bottom of the elbow which is several inches below the surface. This results in less debris getting into the outlet pipe.

Water damage to the house is the serious implication.

Look for evidence of backup at the basin. Check the arrangement of the outlet pipe and the condition of the basin walls, floor and cover. Wood walls will eventually rot, and concrete walls can suffer frost damage. Make sure the cover is not obstructed with debris. The cover must not allow children to fall or climb into the basin. Remove the catch basin cover if it is loosely secured, or look through the grilles. A flashlight often helps. Check the basin for cracked or deteriorated walls and check the size of the outlet pipe and its configuration. Is there an elbow with the inlet facing down? The drain should be at least three inches in diameter. If the outlet pipe is completely covered with water, it may be clogged.