The dry weather flow or the quantity of sanitary sewage depends upon the following factors:

• Rate of water supply 
• Population growth  ​​​
• Type of area served ​​​​​​
• Infiltration of ground water 

​​​​​​​​​​​​​​​​​​​​Rate of water supply   

1.  The rate of water supply to a city or town is a expressed so many capital /day.
2. The quantity of waste water entering the sewers would be less than the total quantity of water supplied. 
3. This extra  water that enter the sewer can be assumed to approximately equal to the water lost in consumption. 

 Population growth​​​​​​​

1.   The quantity of sanitary sewage  directly depend on the population. 
2. The sewage quantity with will be produced in the town due to future development of the town and  population should be taken into account and possible accurate result should be obtained. 

 Types of area served 

•  The quantity of sanitary sewage also depend on the type of area to be served it is residential,  industrial or  commercial. 
• The quantity of sewage produced in residential areas directly depend on the quantity of water supply to the area. 
• The quantity is obtained by multiplying the population with this factor. The quantity of sewage produced by various industries depend on the various industries,  and it is different for each industry.

Infiltration of Ground Water 

1.  Groundwater or sub-soil water may Infiltrate intothe sewers through  the leaky  joints.
2. Both Infiltration as well as ex- filtration are undesirable and take place due to imperfect joints. 

 Conservancy system

1. The system is unhygienic since everything is visible.
2. Due to putrefication, there is a lot of foul smell.
3. Compact house design is not possible.
4. Large labour force is required.
5. Water consumption is small.
6. No technical persons required.
7.  Acute pollution problems.            

Water Carriage Systems

1. The system is hygienic. Sewers are laid below the ground and hence excreta etc. Is not visible.
2. No changes of putrefication and hence no foul smell.
3. Compact design is possible .
4. Labour force is negligible small.
5. Required high water consumption.
6. Technical persons required.
7. Pollution problems are rare.

Every community produces both liquid and solid waste. The liquid portion waste water is essential the water supply of the community after it has been found by a variety of uses such as spent water from bathroom, kitchen, lavatory basins, house and street washing, from various industries processes semi solid waste of human and animal excreta, dry refused of house and street sweeping, broken furniture, waste from industries etc. It also contains nutrients, which can stimulate the growth of aquatic plants and it may contain toxic compounds. Therefore, in the interest of community of the city or town, it mist essential to collect, treat and dispose of all the waste products of the  city in such a way that is may not cause any hazardous effect on people residing in town and environment.

1. Due to high strength to weight ratio,           steel is at least 3.5 times more efficient       than concrete.  To replace one unit area     of steel in tension (with yield stress of        450 Mpa), the equivalent concrete (M30)    area required may be about 200 units. 

2. Steel offers much better compressive       and tensile strength that concrete and         enables lighter construction. 

3. The quality of steel construction is            superior., where as quality of concrete        construction may be affected by poor          control of water cement ratio and curing. 

4. If reinforcement in concrete structures       corrode, it is extremely difficult to repair     and restore them to the original                    condition; where as steel members is          easily repairable at almost any stage of      corrosion. 

5. Unlike reinforced concrete, steel can be      easily recycled and can be used as               another product without losing its quality.