What are the things that we should keep in mind while inspecting or doing venting of any appliance such as water heater or furnace?
Clearances to building openings (Clause 8.14.8) and clearances to regulators (Table 5.3).
You also want to refer to the installation manual for how the termination is configured and to ensure the vent lengths and vent sizing are correct.
Some non-direct vent water heater's above 50,000 BTUs would also require an outdoor air supply. (Clause 8.2.3).
Most important is separation on termination points. Most need a 12 inch separation