Plastic Sewer

The use of plastics for non-pressure sewer pipes is of comparatively recent origin and is still in the experimental stages. 

However, some countries, such as the Netherlands, Scandinavia, France, etc., have already begun to use plastic pipes for sewers of 250 mm dia and above on a moderate to large scale (15% to 25% or so).

Their use is hardly 5-7 percent in Germany and the United Kingdom, and almost no plastic pipes are used in India for laying sewers, although, they are increasing the use of plastic pipes for internal water supply and drainage fittings.

In addition, plastic pipes of up to 1.50 mm dia have also begun to be used in house connections in India to carry sewage to the municipal sewers. 

Although, the use of plastic pipes for non-pressure sewers is not very promising, however, advanced plastic technology has increased the use of plastic sewers.

The test results on uPVC pipes have shown that:

• These pipes continue deformed for about two years; the deformation rate decreases over time.
• Its deformation is mainly influenced by the type and method of application of the backfill material.
• Traffic loading has a little effect on the final deformations, but it reduces the time to achieve equilibrium conditions; and 
• Due to excessive deformation, a PVC pipe failed to operate as part of an operational sewer system.

The most advanced development of a rib-reinforced solid wall uPVC pipe (ULTRA- RIB), which has been largely tested in the U.K. and Scandinavia, has shown very much satisfying results.

Read Also:

 Types of Sewer

Brick Sewer

Steps Of Laying Of Sewer Pipes

Precautions to be Taken While Entering Sewers

Various poisonous and explosive gasses are commonly found in sewers such as hydrogen sulfide (H2S), carbon dioxide (CO2), and methane (CH4) along with petrol vapors. These gases are produced largely when the sewage becomes stale and septic, which occurs more commonly in hotter climates.

In addition to the production of these harmful gases, oxygen is consumed by the organic matter for their decomposition, resulting in a lack of oxygen inside the sewer and can, therefore, cause difficulty in breathing.

Various methods are adopted for ventilating the sewers in order to avoid the large-scale presence of these poisonous and hazardous gases inside the sewers. In addition to the ventilation of sewers, the following precautions should also be taken while allowing the workers to enter the sewers: 

1. The very first precaution which should be taken before entering a sewer through a manhole is to open the covers of the manholes; at least half an hour in advance. This will help in obtaining some ventilation and exposure of the sewer to the atmospheric oxygen.

2. Tests should be conducted in order to identify the presence of any harmful gases inside the sewer. The following tests may be carried out to detect their presence.

• The first test is performed to detect H2S gas present in the sewer.
• The second test is performed to detect CO2 gas present in the sewer.
• The third test is performed to detect CH4 gas present in the sewer.

3. If the above hazardous gases are absent, a lighted lantern may be lowered down the manhole, so as to test the presence of oxygen. If it burns brilliantly, the sewer can be safe to enter.

4. In any case,  the staff who go down into the sewer for inspection must be bound to their waists with ropes and held them fast by persons on the top so that they can be pulled up quickly in case of any risk. A responsible officer should be available to handle the operations perfectly.

5. It is strictly prohibited to smoke or bring open light inside the sewers.

6. Necessary indicators of alert should be set up.

Read Also:

 Methods of Ventilation in Tunnels

 Method of Ventilation of House Drains System

 Purposes of Ventilation in Buildings