Systems and methods of disinfection of catheter connections are provided. A transfer catheter connector can include a UV-transparent window at its distal end and a seal proximal to the window. A solution set connector can be inserted inside a portion of the transfer catheter connector to connect a solution set and transfer catheter. The solution set connector comprises a lumen covered by a leading membrane surface； and a sealing surface configured to sealingly engage the window surface. The connectors can be connected in a disinfection position configuration in which flow is not permitted between the catheters and the connectors are irradiated with UV light. After disinfection, the connectors are advanced to a flow position in which the piercing member pierces the membrane surface, enabling flow between the catheters. The system comprises clips that prevent advancement to the flow position without interference by the disinfection unit or by a user.
