Cindy
A lot of AHJ's have told me that the NEC stopps at the outlet. If the EC did not install the tanks or the tank equipment, it's not the EC's responsibility.
While we can advise, we cannot control some one else's actions.
Personally I would have recommended GFI breakers for the set up you described in writing. If the owner said "ok" then installed them, if the owner said no then file the answer and keep that with the job records.
The NEC does not say any thing about this or any other planned decoration installed after our work is done.
