Drum type washing machine and operating method of the same

A drum type washing machine, comprising:

• a tub having an air hole permitting fluid communication between an inside of the tub and an outside of the tub, the tub configured to hold water;
• a drum inside the tub, the drum configured to accommodate laundry and rotate;
• a water pressure and/or level sensor configured to sense a level and/or pressure of water in the tub;
• an air flow path connected with the air hole of the tub and configured to permit fluid communication between the inside of the tub and the outside of the tub;
• a bubble detecting sensor along the air flow path, the bubble detecting sensor configured to detect bubbles, suds or foam, wherein the bubble detecting sensor comprises a bubble sensing chamber installed along the air flow path between a first hose and a second hose, wherein the first hose is connected to the air hole and the second hose is configured to guide water discharged through the first hose along a discharge flow path, wherein the bubble sensing chamber is configured to collect water and/or bubbles discharged from the first hose;
• and
• a controller configured to perform a bubble removing procedure according to an indication of the bubble detecting sensor, wherein the air hole is formed at an upper portion of a rear wall of the tub,
• wherein the second hose branches into a third hose and a fourth hose, wherein the third hose guides water discharged through the first hose along a discharge flow path and the fourth hose discharges gaseous and/or fluid from the inside of the tub and the outside of the tub, wherein the first hose, the second hose and the third hose are installed along the circumference of the rear wall, wherein the fourth hose is installed toward the upper portion of the rear wall.