I am concerned about spillage and backdrafting of water heat, but to install a power-venting unit requires PVC to be run through my house.
The utility closet is in the center of the home. I am trying to figure out if there are hot water heaters which use metal exhaust piping that are power vented or some alternative that is more cost effective.
You can install a draft-inducer fan on an existing metal flue. Most HVAC companies should be able to do this and it should not be very expensive. They are wired to the system to come on any time your water heater is running. Another option is to bring combustion air to the utility closet.