Water Heater Hookup

I plan to change out my 40 ga. electric water heater in the next few days. The new heater has dialectric heat traps installed.
I replaced my existing supply lines, about one month ago, with steel braded ones that seal with an "o" ring.
The dielectric fittings on the new heater have a plastic sleeve that presses lightly inside the opening.
It appears to me that if I use my existing supply lines, the "o" ring will seal against the plastic and not the metal. Water can exit between the plastic and the bore of the fitting.
Will this type supply line work or do I need something else?

I was wondering about these earlier. IPC and UPC require 12 or 18 inches (can't remember specifically) of metal connecting to the water heater hot and cold. How are these braided supply's legit¿

Have a look see at this spec sheet.
UPC and NSF say okay...
http://www.watts.com/pdf/ES-CWH-S.pdf

3/4" Dielectric Union Females will thread right onto those dielectric nipples, then hard pipe that back to the rest of the house, the way it was designed to be.

If you're in Ca, that doesn't apply in earthquake land.