I'd like to install a new Electric hot water heater and to keep my current water heating system in the case that I need it as a back up. The current system is a oil burner with an internal coil for the water to pass thru to heat, then the water goes to a mixture control valve etc. Is it possible for me to plumb in an electric hot water tank into the current system by using shut off valves and TEE connections? or is this a not-so-good idea? Any advice is appreciated. Thank you in advance.