Where a French drain ends

Step by step

1. 1Perforated run. Up at the wet end the pipe is perforated and bedded in washed rock, holes down, wrapped in filter fabric. Along this stretch it is doing one job: collecting the groundwater that keeps the driveway soft.
2. 2Turn to solid. At the low end the perforated pipe turns to solid pipe. This is the part that gets missed. Perforated pipe leaks along its whole length — keep it going and the water you just collected drains straight back into the ground before it ever reaches the outlet.
3. 3The fall. The solid pipe carries the water away on a steady fall of at least 1% — about ⅛ in per foot. The dashed line is dead level, so you can see the pipe dropping away from it the whole way.
4. 4Level spreader. It ends in a level spreader: a shallow rock-filled trench dug ON THE CONTOUR, dead level end to end. After a whole run built on fall, the last two metres are deliberately flat.
5. 5A sheet, not a stream. Because the spreader is level, water fills it and spills over the whole length at once — leaving as a thin sheet across vegetated ground instead of a jet that cuts a channel. The outlet sits lower than the pipe, on your own land, well back from the property line.