A treatment apparatus for treating closures for containers. The treatment apparatus includes a box-like body and a treating chamber inside the box-like body. The treating chamber configured for treating the closures. The treatment apparatus further includes a dispensing pipe located inside the treating chamber and configured to dispense a sterilizing substance and a supplying circuit configured to supplying the sterilizing substance. The supplying circuit including a feeding line, a main line, and a secondary line. Both the main line and the secondary line branching-off from the feeding line and the main line emerging into the dispensing pipe and the secondary line emerging inside the box-like body. The treatment apparatus further includes one or more valves operatively active on the supplying circuit to establish a selective fluid communication between the feeding line and the main line or between the feeding line and the secondary line.