Litters ranged from 12 -17, with 14 being quite common. 3 weeks gestation, 3 weeks to 40 grams, one week rest for the female, then back with the male for two weeks. I never really kept good track of the numbers/time frames, but always had rats on hand. The drinking valves came from here: www.agselect.com/ED/showdetl.cfm?&DID=11&Product_ID=179&CATID=12
I rotate the females in and out of the males bin. One male, 3 females is what I started with and ended up with 5 females, as I built a new rack and added some bins. I can hold 8 bins now, but currently they are all empty. I will probably start up again this fall. The auto watering system is the BOMB. Just fill the large container when it needs it, and I add a couple teasSpoons of bleach.
I know this thread is a bit old, but wanted to add a feeder-growing system I came up with a couple years ago. I breed ball pythons, and always need a steady supply of mice, rats, and soft furs. I used these feed troughs to grow my soft furs to appropriate feeder size, but see no reason why someone couldn't get a good rat colony going in one.
The troughs themselves were 4x2x2, from the local feed store. I drilled a hole near the bottom in each, to accommodate the automatic watering system valves. In theory the sides were too high for rats to jump out, but I went ahead and built some simple screen tops to make sure they stayed in. Feeders were made from pig feeders with the trough parts cut off and 1/2" wire attached so they could eat through.
Worked great during the time I used it, and I plan on setting up some more of these once I am again able.