Z-Flex 4" Universal Appliance Adaptor with Back-Flow Preventer & Condensation Drain (2SVBFDPA04) 4" Universal Appliance Adaptor with Back-Flow Preventer & Condensation Drain For Takagi, Paloma, Rheem, Noritz, and Bosch AquaStar 240FX and AquaStar 125FX Useful in colder climates to prevent cold air from flowing back into your heat exchanger Condensation drain provides a 3/8" drain point