No problem tiny, your very welcome. As to hydro growing, yes you have to know exactly what your doing, there really is alot more too it, but it is WELL WORTH THE REWARDS!!
As to the water pump back up battery. Yes that is crucial. my uddy had a 2 plant hydro setup, and a snow storm hit, and he lost power for 2 days. All his plants died. After seeing that i have always made sure that i have some form of backup power to my grow.
I have a car battery in my closet, with the wires running to the PC case under the carpet. Its on a electric couple switch. Basically if the EC senses a change or absence in electrical current it will then draw electricity from the car battery.
if you will give me the deminsions of your growing space, and the tubs, I can draw you up a diagram and a materials list for your 4-6 plant 2 res. DWC setup. then you should have no problem getting it set up. Let me know in a pm if you would like.