Method for introducing liquid into flow path device

A method for introducing a liquid into a flow path device, the method comprising:

• preparation including establishing a connection between a flow path device and a switcher to allow a liquid flow between a second opening in the flow path device and a first port in the switcher, the flow path device including a flow path portion inside the flow path device to allow a liquid flow between a first opening and the second opening in the flow path device, the switcher including the first port, a second port, and a third port and being selectively settable to one of a first state, a second state, or a third state,
• the preparation including establishing a connection between the second port and an internal space of a liquid storage to allow a liquid flow between the second port and the internal space, the liquid storage storing a first liquid,
• the preparation including establishing a connection between the third port and a suction-discharge unit to allow a liquid flow between the third port and the suction-discharge unit, the suction-discharge unit being configured to suck and discharge a liquid,
• the preparation including establishing a connection between the first opening and a liquid feeder to allow a liquid flow between the first opening and the liquid feeder, the liquid feeder being configured to feed a second liquid different from the first liquid,
• the first state being a state allowing a liquid flow between the first port and the second port,
• the second state being a state allowing a liquid flow between the second port and the third port,
• the third state being a state allowing a liquid flow between the first port and the third port;
• filling after the preparation with the switcher being set to the first state, the filling including feeding the second liquid using the liquid feeder to fill, with the second liquid, a flow path from the liquid feeder through the first opening, the flow path portion, the second opening, the first port, and the second port to the liquid storage;
• first suction after the filling with the switcher being set to the second state, the first suction including sucking the first liquid using the suction-discharge unit from the liquid storage through the second port and the third port into the suction-discharge unit;
• and
• introduction after the first suction with the switcher being set to the third state, the introduction including introducing the first liquid using the suction-discharge unit into the flow path portion through the third port, the first port, and the second opening.