I have an auto watering system for my rats and can tell you from experience of putting the system together its not nearly as hard as you think its going to be. Before getting all of my equipment I was think how hard this is going to be because I like you couldn't find great instructions to use. I would suggest using the new RBI drinking valve personally. I had the edtsrom valves and they work great but you can save a good amount of money depending on how many you need with the RBI's and they work just as good. The pricing on the equipment doesn't really vary too much as far as the plastic tubing and the tank connector. One piece of advice that I can give you is to order an L fitting for the bottom of your rack. For some reason I ordered a ton of the T's and no L's and was left stringing lines from one rack to the other on the bottom. Also get yourself a good number of clamp loops as they will neaten up the piping and stop the rats or mice from chewing through the lines.

I put the link to the RBI rodent watering page with all the goodies I was talking about above. Good luck and if you need anything else I didn't mention feel free to ask

http://www.reptilebasics.com/rodent-bird-watering