Install new 50 gallon Rheem water heater. Install all code compliant upgrades, including putting stands underneath water heater, pan, dielectric fittings and strapping new thermal expansion tank. Improper venting installed on old water heater. Replaced with new double wall vent. Technician found that gas line ran to heater was track pipe and going through wall, which is a code violation. Technician removed gas line going through wall and re-piped with new black iron. Checked and tested for leaks. Pilot light lit and burner assembly on when technician left