What is a French Drain?

What is a French drain and how does it work?

What is a French drain? A French Drain is installed underneath the basement floor on the inside perimeter of the basement. The French drain A-1 Basement Solutions installs is also known as a Deep Channel Pressure Relief System. This is because it relieves the hydrostatic pressure (water pressure) from the footing area.

The French drain system uses a mechanical pump (sump pump) to remove water from the basement. The water enters the sump pit from the perimeter drains of a basement waterproofing system, and then the sump pump pumps it up and out of the basement.

What is a French drain named for?

The earliest forms of French drains were simple ditches, pitched from a high area to a lower one filled with gravel. These were described and popularized by Henry Flagg French (1813-1885) a lawyer and Assistant US Treasury Secretary from Concord, Massachusetts in his book Farm Drainage. Mr. French was very proud of his cellar drainage system where he surrounded a drain tile with gravel and kept his cellar dry.

What is a French drain used for today?

Henry Flagg French built his system with clay pipe and today we use High Density Polyethylene (HDPE) pipe, but it is still essentially the same system for the last 160 years or so. No one has made a better French drain in all these years, so it is still in use today.

Installing a French drain around the inside perimeter is most commonly done after the house has been built. Most often, this is done in response to a wet basement or right before performing a basement finishing.

To install this kind of drain:

  • The inside perimeter of the floor is cut approximately one foot from the wall. A trench is excavated and pitched.
  • Where possible, the lowest course of block is tapped and bled (weep holes) in order to drain the walls.
  • Fully slotted polyethylene drainage pipe is installed and covered with gravel. This pipe meets the requirements for drainage pipe as required by the State Code and the standards for ASTM-F405-74.
  • The basement floor is re-cemented to its original level.
  • To discharge the water, we will install a submersible pump in a covered polyethylene liner.

The A-1 Basement Solutions French Drain is usually installed in 1 day by A-1 Basement Solutions experienced staff. The system is maintenance free once installed. An interior French drain is much less likely to clog than an exterior, partially due to the fact that it is not sitting underneath several feet of soil.

The French Deep Channel Pressure Relief System carries a transferable lifetime Guarantee. There is no tax of any kind as this is a Capital Improvement to the home.