[LazyPup]

There are a couple more points you should be aware of when installing a water heater in an attic space.

When a water heater is installed in an attic space, the physical location of the water heater may be no more than 20' from the attic access door.

The attic access door or hatch must be large enough to pass the water heater through it. (under the IRC the minimum hatch or door size is 22"x30"; Under the UPC the minimum is 30"x30")

An electric water heater is required to have an "electrical service disconnect" in the near proximity and in direct line of sight from the water heater. (Exception, the breaker may be used as the service disconnect if it is in direct line of sight from the water heater location).

In your situation the correct placement would be to install the service disconnect where you are presently planning the junction box.

Code requires a minimum of one light fixture in the near proximity of the water heater and the switch to control that light must be within 6' of the access door to the attic space.

Code requires a 120v duplex receptacle in the near proximity of the water heater.

The water heater is required to have a drip pan & the drip pan must have a 3/4" drain line that terminates into an approved waste receptor or it must terminate outside the structure. Under the IRC the point of termination must be not more than 6" above average terrain. The UPC permits the line to terminate ata point greater than 6" but not more than 24" above average terrain.

The T&P valve must also have a full bore line the same size as the T&P discharge port and it must terminate the same as the pan drain.

The T&P MAY NOT terminate into the pan and the pan & T&P drain lines MAY NOT be combined into a single line.