Had the same issue with the hum upstairs when I replaced my electric water heater with a power vent gas one after getting natural gas in my neighborhood. The PVC vent pipe attached directly to the joists by J-hooks (I originally routed it to follow the furnace vent as you have) conducted the hum to the house structure, and the hum was horrendous upstairs. The solution was to re-do the vent with polypropylene vent pipe (I used Centrotherm pipe). Since the polypropylene is lighter and not as stiff, it doesn't transfer the hum/vibration nearly as much. And it is rated for higher temperatures than PVC (230 F). The hangers should have rubber or soft plastic around the pipe to dampen the vibration and not transfer it to the floor above. You can also put fiberglass pipe insulation around polypropylene pipe to dampen the hum further (DON'T do that with PVC as it would overheat). Most importantly, rerouted the vent to make it as short as possible (it shouldn't come out so close to the furnace air intake anyway, as exhaust fumes will get sucked into the furnace intake). Now I can barely hear it upstairs. Still, no matter what you do, these things are noisy. My next one will definitely be a tankless.
Nice clean work, Mark. Hopefully you put a trap on that condensation drain. A simple loop filled with water will keep the dangerous exhaust from blowing into your home. Also to be more specific: I believe your old water heater was an atmospheric vent not a direct vent as the last commenter stated and yes, the new is a power vent. A direct vent would have a separate intake that comes from outside the house.
The exhaust needs to terminate a min 12" above the intake exiting the house. Also, a min of 4' distance is standard to any gas/electric meter. Both pipes should terminate further to the right. And putting a TEE over the intake (vertical orientation) is recommended to prevent wind gusts tripping the pressure sensors. As for the blower noise, will probably require insulation in the basement ceiling. Unlikely to be related to the pipes themselves though.
This is why i hate the power vent hot water heaters and furnaces, you can hear that shit blowing and buzzing through the whole house. I'm trying to stick with my direct vent, natural air exchange style A lot of people bitch and whine about not doing it right, I do this same stuff, I'm not a plumber, a welder, an electrician, a gas fitter, or HVAC specialist, or even an auto mechanic, a landscaper, or gardener, or a concrete finisher. But I do it. I do it the way it works, and if someone bitches about how I do it, they can politely fuck right off, because its done and its working. I have the smarts enough to know when I am in over my head and should require the services of a professional. Good work on this project. water heaters can be real assholes.
