A gravity fed water system is a little expensive initially, but believe me it's worth every penny and then some compared to filling individual water bottles every couple of days. If I had to give up my watering system and go to bottles, I'd probably just quit breeding rodents.
Installing the system is pretty simple once you see the parts. You can see pics of how I installed it on a couple of racks on these pages:
http://www.arbreptiles.com/cages/rat_rack/ratrack.shtml
http://www.arbreptiles.com/cages/rat...ing_rack.shtml
Just scroll down a bit on both pages to the watering system section.
As for parts you'll need the following:
A bucket of some sort, preferably translucent so you can see the water level through the side.
A supply valve for the bucket.
One drinking valve per tub. The Vari-Flo valves are usually recommended for mice. I've used the standard non adjustable valves for both mice and rats though so either will work and there's no price difference.
One Tee fitting per tub except for the last one. You can use a 90 degree fitting there or just bend the tubing which is what I do.
Enough 3/16 tubing to go through the rack.
Some loop clamps are handy, but some people use electrical staples and just put them in carefully so as not to crimp the tubing. I prefer the loop clamps myself.
The cheapest place I've found for the parts the last time I bought any was at Klubertanz Equipment.
http://www.klubertanz.com/
The part numbers for the components are:
Supply valve - A202
Brass Vari-flo valves - A301
3/16" Tee - A405
3/16" tubing - A401
Klubertanz does not carry the loop clamps, I get those from AG Select here
http://tinyurl.com/43ub8h
These are the parts and brands I use, Edstrom.
One thing I notice, the way you have built the rack using water valves will either require that you slide the tubs out until they hit the valves then compress them a bit until they drop out, or shorten the slides they hang on.
Pushing in one side of the tub enough so that it drops out isn't a problem though, I have to do that with my racks.