Im testing it out with water and it just isnt carbonating! Tried leaving the gas on @ 300kPa for several mins, rolling back & forth, rocking back & forth etc, still goes back to 0 and produces a very flat soda water. :huh:
Any ideas?
You can carbonate two ways, or actually three (at least).
One is to simply prime your keg, as you would for bottling and give it a week or so at ~18-22 degrees. Leaves a bit of sediment behind, but doesn't use CO2 (you can also rack early, but takes a bit of judgement).
With CO2, you can just dial it up a bit higher than you want, say 140, leave it for a day or two and then wind it back and leave it for a week or so. All of this cold.
If you are impatient, you can do what you are trying to do -- force carbonate. There would be a few posts on this here if you search. Basically, about 300 kpa for about 5-6 minutes, with the keg on its side and gas in at the bottom, and rocking sufficient to keep the stream of gas bubbling in (you can hear it). If the beer (or water) isn't cold, this ain't going to work.
Even if you do force carbonate, it really takes a week for the beer to settle in in terms of everything blending. If you taste it each day, it will change.
There's lots of info on here and lots of good books. Read a bit more and then experiment. Enjoy the journey.