Dump bailers for cement, acid, or sand dumping operations are offered in two types—the positive-displacement (PD) bailer and the gravity-feed bailer. Dump bailer uses a weighted swab piston to push, or positively displace, the bailer’s contents into the wellbore. The dump bailer does not use any explosives. Instead, a solenoid drops a weight bar from a set of collets, causing a pressure wave that moves a piston in the bottom of the bailer to release the cement. This advantage helps to make the system technically superior to other positive-displacement systems in the industry. The gravity-feed system is the most commonly used dump bailer in the industry. The gravity-feed system requires explosives to shatter the disk in the bottom of the bailer, enabling the cement to flow.