Thetford Vacuum Breaker 34122 (Aqua Magic Style II, Style Lite, Style Plus, Residence)
This vacuum breaker is used for Thetford models Style II, Style Lite, Style Plus, and Residence. If you have a fresh water leak issue it could be this part or the water valve. The best way to check is to wrap some tissue paper around both parts and flush the commode. It's tricky to determine where exactly the leak may start but this is good tip for troubleshooting.