When level reaches 30 %, check the operability of the reactor discharge valves opening in manual, one at time, LV 4001A/B at 10% and after that the relevant upstream piston valve for few seconds, checking if the filter level increase.After the check, select the discharge line to be in operation and put the level controller in AUTO with set point around 50 %; when the level reaches the set point value, the relevant piston valve can be opened.