French Drains and Their Modern Successors

By Marlin Breems, Varicore Technologies

 

Workers take care to install the underground channel for an APO Polymer system at the correct slope to insure proper drainage. Once in place, a grate will be placed over the trough at the project?EUR??,,????'???s surface level. Smaller versions use the same design for suburban backyards and hardscapes. photo courtesy of Aco Polymer Products Inc.

The term ?EUR??,,????'??French Drain?EUR??,,????'?? is used to refer to shallow subsurface drainage in landscapes, parks, golf courses and athletic fields. People use the term with a wide variety of meanings, however. The exact meaning varies from one geographic region to another and the meaning has shifted with the passage of time.

Evolution of the French Drain

No, the French drain is not some exotic European drainage method. Although the method, as well as the term, is widely used in Europe, it originated in 19th-century New England. It derives its name from Judge Henry French from Concord, Mass., who published a book called Farm Drainage in 1859.

Stage 1: French Drain

Early French drains, and some still today, were merely egress trenches cut through low lying wet areas and filled with gravel, crushed rock, or fragments of brick.

Stage 2: French Drain

Placing a clay drain tile or a slotted or perforated plastic pipe at the bottom of the gravel-filled trench dramatically increases the flow rate. The water-saturated aggregates readily transfer water to the drainage pipes, which in turn provide a speedy escape path. Although the flow rates differ considerably depending on the size and type of drain tile, all provide flow rates far superior to a simple rock-filled trench.

The DeWitt D-Drain is designed to keep silt and sediment away from openings for water flow. The filter fabric (on top in this view) will be placed towards the incoming water. The ?EUR??,,????'??cleats?EUR??,,????'?? in this view create open space for water flow between the fabric and the drain itself. photo courtesy of DeWitt Co. Inc.

Mitered Drain?EUR??,,????'???s sloped-grate design comes in a variety of sizes for different flow capacities. The sloped design helps keep water flowing and keeps blockage at the inlet to a minimum, the manufacturer says. photo courtesy of Mitered Drain, Inc..

Stage 3: French Drain

To address the issue of life expectancy, installers began the practice of lining the trenches with a geotextile filter fabric. These drains were also generally more selective in their use of backfill, usually requiring uniform crushed rock.

Contemporary Drainage Systems

A variety of drainage systems now on the market seek to address the inevitable clogging-up of the traditional system. Varicore?EUR??,,????'???s Multi-Flow system uses multiple polyethylene flow channels wrapped in a geo-textile fabric. The system is typically installed in a four-inch wide trench and embedded in clean coarse sand. ACO Polymer Products, Inc. manufactures a range of covered trench-drain products that can be uncovered and cleaned to restore their water capacity. The systems are used at stadiums, on airport tarmacs, in residential settings and elsewhere. Mitered Drain Inc. markets a simple, somewhat different design that runs drainage pipe at a slope for water flow directly from problem areas. The system is useful for channeling runoff directly to bio-swales and detention ponds. DeWitt Co. Inc.?EUR??,,????'???s D-Drain is a molded drainage core that is wrapped in filter fabric and designed to resist clogging. Like the other systems, it is compatible with a variety of custom fittings that help designers tailor drainage for specific sites.