When a new connection is required into a NYC sewer and no connection is available, the most usual connection required is a drill in. This is performed using a core drill machine. It is not permitted to chop into a NYC sewer using hand or power tools.
A hole is carefully cored through the NYC sewer a specific size larger than the pipe size to be connected. In most cases the city sewer must be prepared before the core drill is done by encasing the public sewer in concrete. In other cases a concrete cradle must be installed under the public sewer. The concrete reinforces and strengthens the city sewer from the added stress of the core drilling and the future house connection
A riser connection is a vertical connection built on the top of a city sewer for use as a connection for a house sewer. Depending on the size and type of the public sewer different designs are used in the construction of a riser. When a sewer riser connection must be built it is a multi-step and fairly costly process.
It is usual for a riser connection to be required when the depth of the public sewer is greater then 13′. A riser connection can also be required if a groundwater or a rock condition exists. In these cases it is meant to alleviate the cost to property owners of having to excavate to great depths, or through groundwater and rock, in order to connect properly to the main sewer line. If a future sewer repair is needed, a riser also lowers the cost at that time as well. A riser is also required when the difference in elevation from the point where the house drain exits the building to the city sewer is greater than the pitch that is allowed to be used. As sewers work on the principal of gravity, pitching the pipe is used so the waste-water runs off properly.