I set up our waterer yesterday and put all five nipples I ordered in a five gallon bucket for the outside covered run. I am going to order more nipples for the coop and probably will only put in two or three in that one. Five is probably overkill for 6 chickens but I am new to this and did not want to have any of the girls not get to water when a couple of the other chickens were under there getting a drink. So far, so good...
I was told one nipple per 10 chickens but with a minimum of 2 (in case one gets blocked or something). I installed 3 on the bucket because three is optimized space-wise and I wanted to put a block under one for my varied-age chicks. I've never seen them use more than two nipples at once and they often prefer to share a nipple if two or three are thirsty at the same time. I only installed one nipple in their outdoor bucket and the 10 of them share it just fine (at least, I haven't seen anyone return to the coop for water).
For one to five birds, one nipples.
For five to thirty birds, two nipples.
One per fifteen or less after thirty.
Chicks less than ten days old, double the number of chicks per nipple above.
More than three nipples on the bottom of a 5 gallon pail is more than can really be used by the chickens due to space and their resistance to the idea of standing under something where their view is blocked. Remember that chickens are a prey speices and they are always more comfortable with a verticle avenue of escape.
Never let the possibility of a nipple becoming clogged enter into how many nipples you have for a group of birds. Actually underutilization of nipples can be more of a problem. Constant usage allows solid particles in the water more chances to flow out with the water streem and not block the nipple stem open. If you are going to have problems it will be with over flow.
Here are some pictures of our 3 in the brooder with theirs right now...will update when they move out and we make the new waterer in the coop
They took right to it with no problems and sooooo much easier and cleaner