I encountered one bug (at least) and probably a mistake. The little water purifier (1.25m) is not working at all. I tried to put it elsewhere on my craft in order to see if that was because of some strange "resource flow" but nope. I used alternate resource panel to check if total remaining time was changing when i activated it but no. Carbon recycler (1.25m) works correctly, therefore there is a bug on (at least) the little water recycler : it does not consume waste water neither produce water (i'm not sure about the "does not wonsume" part).
Another problem : recyclers description is saying that they are suited up to X kerbals (8-9-10 for 1.25-2.5-3.75m). I may not understand how this is supposed to works, but i have 5 kerbals, a little 1.25m water recycler, but it does not consume the wasteWater produced by the 5 kerbals. (Of course, i'm using default values).
So, obivously, i suppose that either recyclers description is unclear, or default values are erroneous.
Edit: after more tests, it seems the recycler was not working for some special reasons. Sadly, i don't know why, but when i restarted the game, progressed (used hyperEdit to give me some water in order to complete mission), decoupled some part... (sum up : later, with lots of modifs) i restarted it and this time, it was working. I can provide a save with the bugged craft if needed.