main thing with hardwall is you cant get an accurate reading as the flow bottle on the powercoat only goes to 315 so you just need to keep opening the tap, maybe for the first time put the water pipe that connects to the mixing chamber into a bucket (just so you don't overfill mixing chamber with water) and turn the water up to 315 then turn the tap another 2-3 times then reconnect your pipe and go through the rest of your set up procedure when the material starts coming through you can then adjust the water either way til your happy with it but just try to remember how many times you turned the tap to set material just to make it easier for next time, you'll also probably find you will need a bigger spray cap as think you may only have the 10mm ones that came with machine and as you have barely used yours im guessing there not worn very much, if your around the basildon area at all come and see me ive probably got a nice worn 12mm cap that would be better.
if your intending to spray hardwall all day then you would want to consider stopping at some point and having a quick clean out, and also you need to check your bottom pressure plate after a couple of days as you will get a build up of material in there.
you want your water off the top inlet as well,