I have a cabin in California mountains and it is difficult to get any contractors up there. I have to do most work as a owner/builder. I have an electrician coming up to setup the electrical for a water heater. I've never had an electric water heater in the cabin. He is going to add a 30 amp DP in my panel and run outside the house and into the small basement where the water heater will be located to a junction box. He didn't mention what type of conduit he will use, metal or plastic and if he will be installing a swtich on the box next to the water heater. What do I need to make sure he does so when the inspector comes out, I'm good? Any direction would be appreciated.