Would like to know if the setup in the attached picture is okay. A new B vent chimney flue was installed. A 80% furnace and a water heater were connected to the B vent as shown in the here attached picture. Water heater is on the right. Furnace is on the left. They connect as shown and the single B vent flue pipe then runs out behind the furnace and up the chimney. The question is can the furnace and the water heater both be connected as shown to the single B vent pipe? Will there be a backdraft back through the pipe from the water heater when both the furnace and water heater are running? Is this safe? Thanks for your help.