Well, I was outgrowing my current rat breeding capabilites using lab-style rodent cages, so I decided to bite the bullet and build some racks. After looking at a few designs I decided on Tim Bailey's design (Thanks Tim!!). I was going back and forth between flex tubing or PVC and was about to go with flex, but Home Depot didn't have the selection of T's and other fittings that I needed for the drip emitters that I had purchased. So... I went with PVC.

The only changes I made from Tim's design besides having to adjust for a larger size tub from Home Depot was adding a drain valve on the bottom and placing some 1/8" hardboard on the sides. I needed the hardboard because the 1" x 2" rails that I got from Home Depot were slightly rounded and I found that every time I pulled the tub in or out, they would catch on the rounded corners and slip out of their grooves falling on the tub beneath them. The hardboard cleared that problem right up, though.

The rats seem happy with the extra room, and it's quite a bit easier to clean and maintain than the lab cages.