While most of NYC is connected to the city sewer system, some areas — particularly in Staten Island and parts of Queens — still rely on septic systems. City sewer connections carry wastewater to treatment plants, while septic systems treat wastewater on-site. NYC has been gradually expanding sewer service to areas previously served by septic systems. If you are on a septic system and city sewer becomes available in your area, you may be required to connect. The conversion process involves installing a new sewer lateral from your property to the city main, decommissioning your septic tank, and obtaining all necessary permits.