Difference between separate system and combined system.
| SI.NO. | SEPARATE SYSTEM | COMBINED SYSTEM |
| 1. | The quantity of sewage to be treated is less,because no treatment of storm water is done. |
As the treatment of both are done,the treatment is costly. |
| 2. | In the cities of more rainfall this system is more suitable. | In the cities of less rainfall this system is suitable. |
| 3. | As two set of sewer lines are to laid, this system is cheaper because sewage and is carried in underground sewer and storm water in open drains. | Overall construction cost is higher than separate system. |
| 4. | In narrow streets, it is difficult to use this system. | It is more suitable in narrow streets. |