Wet Bar Pump Question
When you say "Water heater vent" are you referring to the flue stack off the top of a gas fired unit? If its any sort of exhaust vent from the water heater, you do NOT want to tie into it. If its a vent from a floor drain next to the water heater, you can connect into it a minimum of 6 inches above the floor. I assume your wet bar is in the basement, is there are bathrooms nearby or on the same floor? If you can run to an existing vent horizontally in the ceiling, that would be your best bet.
What state are you in? Under some conditions you might be able to vent out the sidewall as long as you meet several requirements and gain prior approval from the inspector, you can't terminate the vent beneath any door, window or ventilated opening. You have to maintain at least 10 feet horizontally from any door, window or ventilated opening unless you are 2 feet above such opening. In Massachusetts, vent piping extensions may be installed outside the building with prior permission of the inspector and when all other means of venting have been eliminated or are not practical.