A)The sewers are used to convey the sewage and also the storm water.

The material used to construct the sewer is determined by the following factor

1) cost

2)the imperviourshers

3)the durability

4) non corrosiveness

5) the strength

6)the weight

After considering the above points the material to be used for the construction of the sewer is fixed . following material is used for the construction of the sewer

1) The asbestos cement

2) The Brics

3) The cast iron

4) The cement concrete

5) the plastic

6) the stone

7) the wood

The sewers are produced in two shapes as per the requirements

1) the circular shaped sewer

2) the non circular shaped sewers. The non circular shaped sewers have various shapes eg egg shape , u shaped , semicircular shape etc.

B) laying of the sewers:-

Once the material and the shape of the sewer is fixed the main job is the laying and testing of the sewers to get better result.

Steps:-

1) the boring holes are dug along the line of the sewers to check the nature of the land.

2) for better arrangement of the manholes it is better to lay the sewers between two manholes at a time.

3) at a distance of every 7.50m to 15m the central line page of the sewer line driven.

4) it is necessary to maintain the central line of the sewer line. For this purpose two methods are used.

A)the offset line:

On one side the line is marked which is parallel to the sewer. It is called as offset line.

B)The sight rail:

In this two post vertical to each other are given on the ground at a given distance from the central line peg.

If the soil is soft the sewer is supported on a layer of concrete.

Once the sewers are laid in a trench it is necessary to checkup the invert levels of the sewers. For that online rods or traveller is used.