The rotary drilling hose (API7K) is the flexible connector between the top of the standpipe and the swivel that allows for vertical travel. Its lengths are in the range of 45 ft (13.7 m) and over. We generally use rotar.
[pdf] With interchangeable core bits capable of drilling holes from 1.5" to 9" in diameter, operators can tackle diverse pipe materials including vitrified clay, concrete, ductile iron, cast iron, C-900, HOBAS, and PVC/HDPE systems using a single versatile machine.
[pdf] Drill stems must be designed to transfer drilling torque for combined lengths that often exceed several miles down into the , and also must be able to resist pressure differentials between inside and outside (or vice versa), and have sufficient strength to suspend the total weight of deeper components. For deep wells this requires tempered steel tubes that are expensive, and owners spend considerable efforts to reuse them after finishing a well.
[pdf] 
