Hydraulic drilling systems are often operated with a cable-tool spudding machine used to handle the rods. Sometimes a light rotary machine is also used. Rods are often moved using a simple tripod or just by hand.
Hollow rod drilling: A string of rods is rigged with a non-return valve arranged to prevent the contents of the rods lowing out into the hole. When the rods are lifted by the spudder, the water and cuttings are lifted with the rods. When the rods are dropped, the valve opens to allow the cuttings and water to enter the rods through the bit. This forces water and cuttings out the top into the pit.
Jetting rigs: Drilling is achieved by water circulation down through the rods, washing cuttings from in front of the bit. The cuttings low up the annular space and into a settling pit so that the water can be recirculated.
Jetting in semi-consolidated formations may be assisted by using a hammering technique to chop through hard bands. A fishtail-type rotary bit may be used and the pipe rotated to cut the hole. All hydraulic methods require the hole to be kept full of water or mud until it is cased.
