The subsurface field drainage systems consist of horizontal or slightly sloping channels made in the soil; they can be open ditches, buried pipe drains, or mole drains;, also, a series of wells. Drainage system requires several materials to be used such as tiles, pipes, and envelope materials for its better functioning. Envelope materials such as gravel envelop and filter including geotextile filters can be used as per requirement. Various coefficients developed may be used for proper selection of the materials.
Concrete, burnt clay and PVC are the materials used for tiles. Concrete tiles are easy to manufacture and can be transported without breaks. Concrete tiles can also be locally made using simple moulds made of mild sheets. Concrete 1: 2:4 proportions should be used and tiles should be properly cured. Clay tiles should be well burnt and without any defects. Good clay tiles have distinct ring when tapped with metal objects. These have advantage of being cheaper than concrete tiles and also can be used in acid and alkali soils. However, they are difficult to transport without breakage and will not be able to with stand as much load as concrete tiles can take.
Plastics pipes are increasingly being popular for tile drainage. The common material is the polyvinyl chloride and polyethylene (PVC). PVC pipes are somewhat more resistant to outside pressure. Plastic pipes come in both smooth and corrugated types. The smooth pipes are rigid and come in standard length. Corrugated pipes are flexible and come in coils. They can be conveniently be used with tile lying machines. They have greater hydraulic resistance than smooth pipes and hence larger size pipe is required to drain the same amount of water. Circular hole in the corrugation allows the water enter into tile drains. Around 20 holes per 30 cm length are provided. The Use of envelope material increases the effective diameter and hence fewer perforations per unit length will be required to get the desired flow. Pipes require less plastic material per unit length and have greater resistance to outside pressure.