Water storage tank bladder, manufacturing method therefor, water storage tank including bladder, and water treatment apparatus including water storage tank

A water storage tank, comprising:

• a tank body including a first entrance and a second entrance into and out of which water flows;
• and
• a bladder disposed in an interior of the tank body to be connected to the first entrance and into or out of which water flows through the first entrance, while water flows out of or into the interior of the tank body through the second entrance,
• wherein the tank body comprises an upper body including the first entrance and the second entrance and a lower body connected to the upper body, in order to cover an open lower portion of the upper body,
• wherein a welding groove is formed in a lower end portion of the upper body, and a welding protrusion inserted into the welding groove is formed in an upper end portion of the lower body, and
• wherein a burr prevention portion, preventing a welding burr generated during welding from being exposed in the interior of the tank body, is formed in the upper end portion of the lower body.