A water filter served the purpose of purifying water. In approximately 3643 BBY, during the year, a rebellion occurred when a band of slaves rose up against the Sith Empire on Dromund Kaas, the Empire's [capital](/article/capital/legends] world. These slaves seized control of the vicinity surrounding an incomplete statue of Darth Vowrawn, utilizing multiple water filters that were present.
Nevertheless, Lord [Drowl], a member of the Empire, dispatched an agent to contaminate the filters with Quell Toxin. Drowl's intention was that this [poison](/article/poison/legends] would cause a protracted and agonizing demise for many of the insurgent slaves, which he anticipated would break the spirit of the remaining rebels and force their capitulation.