Combined Sewer System	SL NO	Separate Sewer System
In this system, only one set of the sewer is laid and carries both sewage and stormwater.	1	In this system, two sets of sewers are laid for carrying sewage and stormwater separately.
The cleaning of sewers is easy as they are of large in size.	2	The cleaning of sewers is difficult as they are of small in size.
The maintenance cost is less.	3	The maintenance cost is high.
The load on the treatment plant becomes high.	4	The load on the treatment plant is less.
Self-cleaning velocity is easily achieved.	5	The self-cleaning velocity is not easily achieved.
Strength of sewage is less.	6	Strength of sewage is more.
This system proves to be uneconomical when pumping is required for the lifting of sewage.	7	This system proves to be economical when pumping is required for the lifting of sewage.
The stormwater is unnecessarily polluted.	8	The stormwater is not unnecessarily polluted.
The initial cost is less.	9	The initial cost is more as compared to the combined sewer system.
This system is suitable when the rainfall is small and evenly spread throughout the year.	10	This system is suitable when the rainfall is uneven or it is heavy for a short duration.

10 Difference Between Combined and Separate Sewer System