I've been trying to figure out ways to improve my system and have an idea but I wanted to see if you all thought it would work. I picked up two 80 gallon water heaters that I want to use to preheat the water going into our 50 gallon electric water heater. Can I use one side arm for both of the preheating tanks if I arrange the tanks so the T&P valves are facing each other? If that would work would it be best to hook the two 80 gallon tanks in series or parallel before going into the electric water heater? Any thoughts? Thanks.