From that video, I'm sure there is nothing to worry about. Mine will do that from time to time and it's just a way of them expressing themselves, and showing contentment. Lisa, 'tiels do not drink that much, but the amount they drink during a 24 hour period would equate to a human drinking 30 gallons of water. Of course I've got some weird birds here.. Missy, Suzie, Lil'bit, Chirp and a couple of the others only want to drink HOT water. When I say hot, I mean temps that I wash dishes in or almost full stream hot! I've also discovered over time they will not eat anything that is cold. I've tried ice cream, cold foods, even ice, and they won't touch it. Even cold beans or noodles and they immediately back off. The warm foods, (boiled shrimp, noodles, breads, etc) are what they really like, so at suppertime, we offer them whatever we are having, and tonight will be fried chicken. Most of the kids would rather have fried chicken than seeds or anything else they like to eat

(can't say that I blame them either.. Emi's fried chicken is the world's best)
JRM, I have a very new female that was an escapee bird, and she will sit around and do exactly what your bird is doing. I often wonder if they are not just bitching and complaining about something they don't like

Almost like they are talking to themselves.. hahaha.. I'd not worry about it one bit. Jackie (bubbabird) made some good points.. it takes time to understand your companion, and with time you will be able to read his body language, chirps, whistles, and such where you know pretty much what is going on and what he's trying to say. I've only had 'tiels now for a little over 3 years, but I've learned so much by just watching them and reading everything I can get my hands on or everything on the web about them. You'll never regret taking him in..and I'd be surprised if you don't wind up with more than one as time progresses. They need buddies too, but let him bond to you first.
Cheers!
Sam