Filter device and filter method

A filter device for filtering a liquid, comprising:

• an inlet chamber for receiving a liquid to be filtered;
• an outlet chamber including at least one liquid discharge line and does not have a liquid supply line;
• a filter system at the bottom of the inlet chamber, which separates the inlet chamber and outlet chamber;
• a liquid supply line situated centrally above the filter system for introducing liquid to be filtered into a center of the inlet chamber;
• a liquid discharge line in fluid communication with said inlet chamber for discharging a portion of liquid received in said inlet chamber from said inlet chamber without passing through said filter system;
• spiral flow elements increasing in height as they extend from said center of the inlet chamber are positioned above the filter system, and control the flow of the liquid to be filtered so that it does not flow directly to the liquid discharge line;
• wherein liquid to be filtered is flowed into the inlet chamber at said center where it encounters said spiral flow elements, with some liquid passing through said filter system as it flows outwardly through said spiral flow elements, and some of the liquid being discharged, unfiltered, through said discharge line.