Liquid discharge system and filter state determination method

A filter state determination method performed by a controller of a liquid discharge system configured to discharge liquid,

• wherein the liquid discharge system includes:
• a head configured to discharge the liquid, the head having an inlet for supplying the liquid to the head and an outlet for discharging the liquid from the head;
• a supply tank connected to the inlet;
• a discharge tank connected to the outlet;
• a pump configured to cause the liquid to flow, the liquid being in a supply channel for supplying the liquid to the supply tank;
• a first filter located in a head channel extending from the supply tank to the discharge tank through the head;
• a second filter located in the supply channel;
• a first liquid amount sensor configured to detect an amount of the liquid stored in the supply tank;
• and
• a second liquid amount sensor configured to detect an amount of the liquid stored in the discharge tank, and
• the filter state determination method comprises:
• determining a state of the first filter, based on a first change amount or a second change amount, the first change amount being amount of change in a detection value of the first liquid amount sensor in a prescribed period, the second change value being amount of change in a detection value of the second liquid amount sensor in a prescribed period;
• and
• determining a state of the second filter, based on a value or a rotational speed of the pump, the value being based on the first change amount and the second change amount.