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Downspout drain system

French Drains
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The purpose of a French drain is to prevent an accumulation of surface water near buildings and instead redirect the runoff water away from buildings. French drains are also known as drain tiles or land drains. Basically the drain is a trench with a perforated drain pipe covered by rocks and/or gravel. The drain can be left as is or covered with at least one foot (30 cm) of soil. I prefer an 'open' French drain with just the rocks and no soil for two reasons. For one, the trench has to be dug deeper and secondly soil and rocks will mix eventually. If the French drain is to be covered with soil the rocks have to be covered with a nylon fabric weed cloth or geotextile fabric. This is to prevent the soil from mixing with the rocks which would render the drain useless. Please keep in mind that the drain works on gravity and for it to be working properly the trench should be sloped at least ¼ inch per foot.
Another place where French drains should be installed is behind retaining walls to relieve water pressure. Water from downspouts can also be spread over a large area, as shown to the right.

"Open" French Drain

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