In a hole making water, the hammer, at some depth, will be overcome by the head pressure. Drillers then use an aerator subs to help lift the column of water in the inner tube to begin circulation.
The Saver Sub is used to connect the entry side swivel to the first piece of pipe and is attached to every pipe, going in and coming out. This position in the string is subject to much wear, so saver sub was designed to be an inexpensive, easily replaceable part. As such, it is used to protect the threads on the actual pipe and allows for a quick and onsite replacement. Using saver sub offers great advantages, as it is cheaper to change a saver sub often, than to buy new pipe once.
The Inner Tube tester is used by screwing it on to a pipe and turning on the air compressor. If there is a leak in the inner tube, it will be revealed by an air leak out of the drilled hole in the center of the inner tube tester. Once a leak is found, often a set of new o-rings fixes the problem. However, there is a rock lodged in the inner tube and the abrasion has worn out the pipe producing a hole in the inner tube, which effectively scraps the rod.
A Blow Down is used at the surface to redirect the compressed air down the inner tube in an effort to dislodge sample in the interchange slot or rock bit adaptor, which is blocking the sample extraction.
A Bleeder Sub allows for a slow release of annular pressure into the borehole.