Systems and methods for determining when a fluid supply container of a blood processing apparatus becomes empty. The system uses a scale to monitor and detect when a fluid supply container is empty based on the rate of change of the container weight and whether the container weight is below a pre-established threshold, and a controller receives a signal from the scale and controls the operation of a pump to stop pumping when the fluid supply container is empty.

A method is provided for controlling the fluid level in an ebb and flow watering system control bucket that is in fluid communication with at least one fluid holding apparatus such as a plant container with connecting water lines, causing hydraulic delays in changes in the fluid level in the control bucket when fluid is pumped to or from the control bucket, typically from a fluid reservoir. The method involves pumping fluid to or from the control bucket to achieve a target fluid level in the control bucket; upon the fluid reaching the target fluid level, starting a timer for a short period of time to allow for the hydraulic delays, and continuing to pump fluid while the timer runs; restarting the timer and continuing to pump fluid if the fluid level in the control bucket recedes from the target fluid level; and discontinuing pumping if the timer runs for the full period of time.

A drainage apparatus for a filter device may include a housing and a solenoid valve arranged in the housing. A non-return valve may be arranged downstream the solenoid valve. A pressure sensor may be arranged between the solenoid valve and the non-return valve. The pressure sensor may be configured for pressure sensing in a chamber disposed between the solenoid valve and the non-return valve.

A device for controlling flow of a fluid, comprising: a first valve comprising: a selectively openable inlet; an opening; a selectively openable outlet, arranged such that fluid may enter the first valve through the inlet, exit the first valve through the opening, enter the first valve through the opening and exit the first valve through the outlet; a first sensor for detecting a fluid; a second sensor for detecting a fluid, the first sensor and second sensor in fluid communication with the first valve via the opening; a controller for receiving signals from the first sensor and second sensor and for controlling opening and closing of the inlet and outlet in response to receiving said signals, arranged to allow, in use, a fluid to flow through the device by flowing: into the first valve through the inlet of the first valve; out of the first valve through the opening of the first valve; past the first sensor for detecting a fluid; to the second sensor for detecting a fluid; into the first valve through the opening of the first valve; out of the first valve through the outlet of the first valve.