A modular unit has at least one filter (10), pump (12) and cooling unit (14) fluidically connected to each other by a connection module (16) and connected to a tank unit (18). The connection module (16) opens out inside (22) the tank unit with a suction opening (20), together with the cooling unit (14) when the tank unit is connected (18). The filter unit (10) and pump unit (12) are arranged outside the tank unit (18). The modular unit can then be placed on and connected to a tank unit. The cooling unit protrudes inside the tank unit.