Diluted solution production method and diluted solution production apparatus

A diluted solution production apparatus for producing a diluted solution of a second liquid by adding the second liquid to a first liquid, the apparatus comprising:

• a first pipe that supplies the first liquid;
• a tank that stores the second liquid;
• a second pipe that supplies the second liquid from the tank to the first pipe;
• a flowmeter that measures a flow rate of the first liquid or the diluted solution that flows through the first pipe;
• a meter that measures a component concentration of the diluted solution,
• a pressure gauge that measures pressure in the first pipe;
• a pressure regulator that regulates pressure in the tank to adjust a pressure gradient between the tank and the first pipe, so as to control an amount of the second liquid that is to be added to the first liquid;
• and
• a controller configured to calculate a target value of the pressure in the tank that causes the component concentration of the diluted solution to be specified value, based on measured values of the flowmeter, the meter, and the pressure gauge, and that controls the pressure regulator so as to adjust the pressure in the tank to the target value.