The capacity of the water tub is 33L. After setting up the system, you need to fill the tub to its capacity. After that, check the water level once in 3 days. In case the level has depleted just top it off. Ensure that the water level is always above the motor, or else the motor would get damaged. Also, it is recommended that you draw out the water completely from the tub using the syphon provided after very 3 weeks and fill it with fresh water.