TYPES OF SEWER:
The following are the various materials, which are used for sewers.
1. Stoneware Sewers:
The stoneware sewers are also known as the vitrified clay sewers or salt-glazed sewers and they are prepared from various clays and shapes in required proportion, allowed to dry and then burnt in a kiln. A small quantity of salt is added to kiln get glass like glaze on the surface of pipes.
Advantages:
1. These pipes are strong enough to take backfilling and traffic.
2. The interior surface of sewers is smooth and impervious.
3. The overall performance is very good.
4. These sewers are cheap and easily available.
5. These sewers are durable and better resistance to corrosion and erosion.
6. These sewers are capable of withstand hydraulic pressure up to 0.15 N/mm2 and bear a load of soil of about 4.5 m depth.
Disadvantages:
1. These are brittle in nature and may damage in handling or transport.
2. These are not strong enough to allow sewage under pressure.
3. These are difficult to handle or transport because of heavy weight.
2. Cast iron sewers:
The cast sewers possess high strength and they are durable. These are available in sizes from 150 mm to 750 mm diameter. These sewers can resist the action of acids in sewage if the inner surface is coated with paint or cement concrete. The cast-iron sewers are used for following special purpose:
I. Danger of contamination against leakages.
2. Expensive road surface like C.C. can be avoided.
3. Heavy external loads under railway lane, foundation.
4. Under high pressure.
5. The places subjected to considerable differences in temperature.
6. Where the ground is likely to subject to heavy movements and vibrations.
7. Where wet ground required reducing infiltration.
Disadvantages:
1. Cost is high.
2. Transportation and handling is difficult.
3. Cement Concrete Sewers:
The cement concrete sewers may be plain or reinforced. The plain cement concrete sewers are used up to the diameter of 600 mm and beyond 600 mm reinforcement is provided.
Advantages:
I. These are strong and impervious.
2. Larger diameter can be made.
3. Inner surface of sewer is smooth.
4. For attack of chemical and erosive actions the inner surface should be lined with vitrified clay.
Disadvantages:
1. Heavy weight transportation and handling is difficult.
2. Joints should be carefully filled.