1) The main drainage lines should follow the lines of natural drainage.
2) Laterals should be laid along lines of greatest slope.
3) Where possible, long parallel laterals should be used.
4) Drainage lines should be made straight or with gradual errors, sharp curve check the flow of water and coarse silt deposition.
5) Silt wells or traps should be put in low spots.
6) The outlet should be protected from erosion and screened against burrowing animals.
7) In heavy clay soils of flat tops surface drainage is preferred.