Basement Drain Tile – Why Your House Needs It
Basement drain tile is also called weeping tile, perimeter drain, footing tile, and perforated drain, among others. Contractors install drain tile systems around the footings of new construction basements and crawl space foundations.
What is Drain Tile?
Drain tile, when used in a residential application is a system of piping, sump pits and pumps, and possibly storage containers that moves water away from building foundations. It collects groundwater before it leaks into the basement or crawl space.
Sometimes called subsoil drainage or a French drain, some form of this system is used in most parts of the world to keep houses dry.
How Drain Tile Works
Water builds up around house foundations from excess rain, high groundwater, faulty eavestroughs, too much garden watering, etc. The more water, the more hydraulic pressure is exerted on the foundation. Gravity helps increase the hydraulic pressure lower on the foundation.
Installing drain tile around the perimeter of the foundation footings–inside or outside–removes water and relieves hydraulic pressure. Less pressure equals less chance of leaks.
The 4” diameter perforated pipe is covered with crushed gravel. 12” wider than the pipe and 6” higher according to the International Residential Code (IRC R405). The rock helps equalize pressure on the pipe and helps facilitate water percolating through to the pipe.
Water moves down the sloping pipe to a sump pit to be pumped away, into a storage container, or to daylight.
Building Code Drainage Requirements
All construction is covered by some kind of code. The International Residential Code, which has been adopted by 90% of US jurisdictions, is used as the basis of most local building codes and modified to reflect local conditions. Part of the drainage sections states:
Drainage tiles, gravel or crushed stone drains, perforated pipe, or other approved systems or materials shall be installed at or below the area to be protected and shall discharge by gravity or mechanical means into an approved drainage system.
Check your local codes to see what you need for drainage in your area. Soil conditions can vary quite a bit–even in small geographic locations. If in doubt, consult an engineer before building.
Types of Drain Tiles
Farmers started using clay tiles to drain water from fields over 2000 years ago. Americans began using them around 1838. The agricultural drain system was renamed the French drain in 1860 after Henry French wrote a book about them.
French drains and drain tiles are still used in agriculture and residential applications. The reason has not changed; moving water away from one location to another. Although the name is unchanged, the material is much different.
Most Popular Weeping Tile: Corrugated Flexible Pipe
The most popular weeping tile is a four-inch diameter corrugated pipe. The pipe is flexible and has slits cut into it to allow water to enter. The pipe is placed next to the foundation footing and hooked into a sump pit or daylighted somewhere downhill.
A fabric membrane is wrapped around or used to cover the pipe. Some manufacturers make pipe that is already enclosed in a fabric sleeve for ease of installation. After pipe installation, gravel covers it, and then comes backfill soil after the wall is poured.
Note: Daylight, daylighted, and daylighting refer to a pipe terminating above ground. Quite often with a grill to prevent rodents from taking up residence.
Rigid PVC Pipe
Drain tiles around house foundations (and French drains) also use rigid PVC pipe. These 10’ sections have a row of holes on one side. The pipe is laid with the holes facing down, and sections are joined with couplers.
Water enters the pipe through the holes and runs downhill to the sump pit, storage container, or it daylights above ground.
Interior Drain Tile Systems
Builders install interior drain tile inside the footings under the basement’s concrete floor. It’s useful in areas with high water tables or underground springs.
Exterior weeping tile picks up water from outside and carries it away. Heavy rains might overwhelm it and allow water to pass under the footings.
All interior tiles drain water into a sump. The sump water is pumped out of the house to drain overland to a storm sewer. Sometimes they are pumped into a storage tank.
Adding Drain Tile to an Existing House
Although the installation of drain tiles is part of most building codes today, they were not always required. It is not compulsory to add them where they do not exist. You may want to consider adding them if your basement or crawl space has serious leaking problems.
Adding Exterior Drain Tile
Installing drain tile to the exterior of your house requires excavating down to the footings and at least three feet out from the walls. Then you lay the pipe next to the footings and cover it with cloth and crushed gravel.
Sump pits are usually located inside the basement walls and level with the floor. Weeping tile pipe runs through a gap in the footing. It is not impossible to accomplish this. Consider an external sump pit c/w a frost-free access.
Note: While you have the excavation open, inspect your foundation waterproofing. It may need to be repaired or there might not be any at all. Now is the time to fix it.
Adding Interior Drain Tile
Installing drain tile to the interior of a basement with a concrete floor is also no walk in the park. You need to break up and remove about one foot of concrete around the entire perimeter of the basement wall. Then dig a trench about a foot deep.
Then you need to add crushed rock for a bed and install your pipe sloped to the sump pit. You will have to break out more concrete and dig more dirt to install a barrel as a sump pit. Then, add more crushed rock on top of the pipe and repair your concrete floor.
The following YouTube video shows this type of installation. The contractor shows drilling through the footing to drain water. I think it is more simple to install a sump pit and pump the water out to drain overland.