Water filter with extended operational period

A water filter, comprising:

• a housing member connected to a water inlet pipe;
• a cassette member filled with filtration and activation agents, which is located inside the housing member, and which has open upper and lower ends, where a water path connecting the water inlet pipe and the upper end is formed between the housing member and the cassette member, while the lower end is directly connected with the water inlet pipe;
• a center pipe located inside the cassette member for connecting an inside of the cassette member with a water outlet pipe;
• and
• a damper member placed inside the cassette member in contact with the filtration and activation agents, which vertically slides along the center pipe during a filtration operation by the cassette member while keeping contact with the filtration and activation agents, and which divides the inside of the cassette member into an upper filtration chamber connected with the upper end and a lower filtration chamber connected with the lower end, where the water flows through the upper filtration chamber from the upper end and the lower filtration chamber from the lower end alteratively.