Water management is an important part of the design and construction of the home. Keeping water from entering the house is critical to ensure the long-term structural integrity of the building as well as to reduce the chances of mold issues and poor indoor air quality. A complete water management strategy will deflect water that comes in contact with the building envelope and divert that water down and away from the house.

A well-sealed foundation or crawlspace will keep water from entering the home, but to finish the task of water management, you must also create a path for water to flow away from the home and be discharged at a safe distance. Allowing water to collect around the foundation will eventually lead to unacceptable levels of soil saturation and ultimately could overcome any water sealing practices used to protect the foundation.

To carry water away from the foundation, a footing drain system should be installed consisting of a perforated drain pipe (also called drain tile) that is located underground on the exterior side of the footings at a depth below the level of the basement slab or crawlspace floor. The perforations allow any surface or ground water that reaches the footing to flow into the drain tile and be carried away rather than pooling along the foundation wall. To keep the pipe from getting clogged with silt, the pipe is wrapped with filter fabric (Figure 1) then laid in a bed of washed stone that is also wrapped in filter fabric, also called geo-textile or landscape fabric (Figure 2). The pipe surrounds the full perimeter of the house and is laid so that it is slightly sloped, allowing water entering anywhere along the perimeter to drain to a single collection point. That collection point connects to an unperforated pipe that discharges the drain pipe to an above-grade location at least 10 feet away from the foundation or to a suitable alternative such as to a drywell or storm sewer. Or, the drain pipe can discharge into a sump pump located in the floor of the crawlspace or basement. The sump pump will then discharge the water either to daylight or to a suitable alternative such as to a drywell or storm sewer. See Patio Slabs, Porch Slabs, Walks, and Driveways for more information about discharging water away from the foundation.

A properly installed and functioning footing drain system will keep water moving away from the foundation to help maintain a dry basement or crawlspace. Poor installation of the pipe system often prevents it from accomplishing this important drainage function.

  How to Install Drain Tile that Discharges to Daylight

1. Dig a trench large enough to accommodate the filter fabric, drainage tile, and gravel. The trench should allow 6 inches of space around the pipe, which means it will usually have to be at least 16 inches deep and 16 inches wide to fit a standard 4-inch pipe with protective cover. Because the drain tile will be installed at a height that is lower than the bottom of the concrete slab or crawlspace floor, the trench must be at least 10 inches deeper than the top of the footing or slab.
2. Slope or level the trench so that when the drainage tile is installed, water will readily flow to the lowest point (i.e., the discharge pipe).
3. Lay the filter fabric on the bottom of the trench. When complete, the entire drainage tile and gravel bed will be surrounded by filter fabric, so leave ample surplus to ensure there is enough fabric to cover the wrap around over the top of the drain pipe and the 6 inches of rock poured over it.
4. Lay a 6-inch layer of ½- to ¾-inch washed or clean gravel in the trench. It is important that the gravel be free of fines (i.e., clean) because silt and sand in the gravel will eventually clog the drain tile perforations or build up in the bottom of the pipe and reduce the effectiveness of the drainage system.
5. Install the drainage tile. Secure all the connections to make a complete drainage system around the entire foundation. Connect the perforated pipe to a non-perforated pipe that leads to the discharge location. (See Patio Slabs, Porch Slabs, Walks, and Driveways for more information about discharging water away from the foundation.) The discharge pipe must lay at a downward slope and discharge to daylight at least 10 feet from the foundation (Figure 3), or to a suitable alternative such as to a drywell or storm sewer.
6. Once the drainage tile is connected, cover the system with a 6-inch layer of ½- to ¾-inch washed or clean gravel.
7. Wrap the drainage tile and gravel in the filter fabric to further protect the system from silt and sand.

How to Install Drain Tile that Discharges to a Sump Pit

1. Prior to pouring the concrete slab or foundation, establish where the sump pit will be located and extend a piece of 4-inch non-perforated pipe from the pit to the exterior of the house, leaving at least 12 inches of pipe to extend beyond the footing. The pipe should be imbedded in the gravel capillary break below the foundation or slab.
2. Pour the foundation, taking care to not damage the drainage pipe.
3. After the concrete has set, follow the instructions listed above for installing the drain tile, with one exception: In step 5 above, install the non-perforated pipe to lead to the sump pit, as shown in the Figure 4. The sump pump should send the water to a discharge pipe that slopes downward at least 1/2-inch per foot for 10 feet (Figure 5) before discharging the water to daylight or to a suitable alternative such as a drywell or storm sewer. (See Patio Slabs, Porch Slabs, Walks, and Driveways for more information about discharging water away from the foundation).