Direct vent water heaters.
Water heater vent height above roof.
Above the highest point where they pass through the roof surface.
The difference is that a power vent water heater pulls in combustion air from the space around the appliance then uses a fan to propel the exhaust through the vent.
Other issue is the bathroom installation which isn t permitted as well unless the water heater closet is sealed from the bathroom area air tight doors and it has a separate fresh air supply from exterior or other areas of the house that can be used for this purpose.
If it is a natural vent type water heater you can not vent it through the side wall it has to vent above the roof.
At the hottest point in a gas water heater flue the flue vent connector right above the heater top the temperature is not likely to rise above 350 degf.
Used where the midpoint of a gable roof would have more than 7 8 feet of run to the ridge.
The average being about 6 foot.
The 2 10 rule states that combustion vents should terminate at least 2 feet above any part of the roof within 10 feet.
It is reasonable to assume that higher in the flue temperatures are much lower.
Exhaust gases are vented outdoors through a separate vent duct or through a separate chamber of the same pipe this requires a double wall vent duct.
Here is the nfp11 codes.
That would be 30 of rise above the roof at the roof plus the 24 if you.
10 4 1 1 vents installed with mechanical exausters shall terminate not less than 12 in.