Abstract: A filtration device is provided whose body member has a transparent or translucent part (i.e., window) so that a user can directly see the colors of the filtering agents inside. If the colors of the filtering agents are changed due to the loss or degradation of functionality, the filtering agents can be replaced so that the performance of the filtration device is consistently maintained.

Abstract: The filtration device mainly contains a hollow body member having a water inlet and a water outlet at two ends; a number of open-top container members vertically stacked and reliably positioned, inside the body member; and a number of agent members placed inside the container members respectively. Each of the container members has a number of through holes arranged spirally at the bottom so that the water is forced into a swirl as it flows through the container members to make full utilization of the agent members. The body member is sealed by a cover that can be easily twisted close or open. As such, the standardized container members can be easily accessed and the agent members can be easily replaced.