What is a French Drain?

Septic tanks only partially treat the sewage and the function of the French drain is to provide the final treatment before disposal of the effluent.

The insitu percolation test should be conducted on all sites which are to receive French drains.

French drains should not be constructed on sites where:
·         the percolation rate is less than 30 minutes
·         effluent may flow out of the ground due to the contours of or the strata forming such sites
·         the level of the water table is or may be such to prevent adequate percolation
·         other sites may be affected by the presence of such a drain
·         there is insufficient space to accommodate the soaking away of the effluent

French drains should be sited and constructed so as to not to cause the pollution of nay public stream, spring, well or water source that is used, or that could be used for drinking, domestic or kitchen purposes.

They should be located downhill of a water source such as a borehole or spring.  Where the location of such a water source is not possible French drains should be located at least 50m from the water source.

French drains should be preferably constructed along the contour of the soil surface