North Star API Water well drill rods are externally flat drill pipes designed for percussion-rotary water well drilling with DTH hammers. Compare the pipe dimensions and connection prerequisites underneath to pick a configuration for the drilling assembly. Kelly Bars/Rods: When generally thought of separate from drill rods, a “square kelly�?or https://northstardrill.blogspot.com/2026/11/why-double-pipe-drilling-matters-in.html