*PLUMBERSSTOCK EXPERT* responded:
Hi there! Thank you for posting a question under the York S1-02814723000 Condensate Trap. The tube that connects to the middle hole on the top of this trap is the S1-02813307000 Drain Inducer Tube. Please refer to page 3, figure 3 of this Parts Sheet for more information. This York S1-02813307000 Inducer Drain Hose is not yet on PlumbersStock.com but feel free to contact our Customer Service Department at 435-868-4020 from 7 AM to 7 PM MST (Mon-Fri) or through email@example.com. They will be happy to assist you in placing the order anyway. Happy shopping!