Practitioner's Tool / Sewers Comparison

Sewers	Appropriate Use	Relative Cost	Operations and Maintenance	Effectiveness
Sewers for Buildings	To transport wastewater from buildings to the treatment system	Generally low but can increase based on length of pipes, soils, and topography. Cost can be minimized by placing treatment as close to buildings as possible	Low for gravity sewers Moderate for pressurized systems	High - Effective when designed and installed properly
Settled Sewers	Small to moderately-sized communities. Uses smaller pipes and can accommodate variable flows	Moderate for the sewer pipes High when considering the cost of septic or settling tanks at each building.	Low for the sewers High for the septic tanks when considering the required desludging.	High when community programs for desludging are provided
Condominial Sewer	Small to medium-sized communities	Low - Allows sharing of sewer laterals, which reduces cost	Low when communities are responsible for maintaining their own laterals, as they are more careful to operate properly	High when strong community participation and bottom-up planning is provided
Combined Sewers	Larger communities	Moderate – groundwater, poor soils and variable slopes increase costs	Low - Periodic declogging is generally required	Moderate – Generally effective at moving waste away from population centers
Pressure Sewer Pumps	When variable slopes or distances will not allow gravity systems	High - Pump tanks, pump equipment, and the cost of electricity adds to cost	Moderate - Pump systems are generally reliable, but trash traps and screens often require continuous maintenance	High - When installed and operated properly