French Drain Systems

Want to install a French drain system? Want to know how French drain systems work? Our guide gives you the facts & information you want to know.

A characteristic of French Drain Systems for draining a relatively large squelchy backyard involves a network of trenches. That water will take the course of least resistance is a well known fact, and this characteristic of water is utilized to drain water. The trenches are filled with gravel that allows easy passage of water through it. Gravel generally refers a naturally occurring variety of soil that is granular in nature and extremely porous, i.e., there are a lot of gaps between the constituent granules that will allow water to pass through without difficulty. In some cases where this gravel is not readily available then hard granite broken stone of small size is utilized.

Since the trench itself is dug in the soil which will allow water through it, albeit extremely slowly – the cause for the sogginess, the bottom and a part of the sides of the trench are lined with landscape fabric or some other impermeable material so that the water will collect and flow down faster.

French Drain System Network

In a large tract of sodden land a network of trenches must be excavated to effectively drain the water. A system of small trenches – somewhat like a maze, each draining a part of the land, is connected to a larger drain which finally discharges the collected water. The larger the extent of the area to be drained the more complex the network. Since gravity can play a major role in the draining of water from a soggy yard, a French Drain System must preferably be installed so that the trenches slope downhill to further aid the flow of water. The beauty of the French drain system is that it will work just as well if the trenches are laid nearly level. A slope of 1% is ideal in most conditions.

Installing French Drains

The most difficult part of the installing of a French Drain System is in locating the place where the water is going to be let out or the “Outlet” as it is known. The problem is easily solved if there is a natural drain in the vicinity; the main drain of the system could be laid to flow out into this drain or channel. This is possible if the tract of land involved is out in the open like in the country side. The locating of the outlet becomes more complicated if the land is surrounded by neighboring properties or when it is situated in a township as this will involve very careful planning. In this case the planning, design and construction of the French Drain System is best left to professional agencies.

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