If you know an athlete has taken a hit to the head, it is NOT your call, you don't get to decide if they go to the trainer. Unless you are a qualified health care professional you are not qualified to call injuries. There is no gray area. If you do your water fountain technique and the athlete has a head injury and you let them back in serious injuries can happen. If they did you would be responsible. It is a coaches legal duty to send an athlete to the trainer if they have hit their head or it is reckless misconduct and negligence.
Times have changed coaches, there are trained cheer safety experts recognized by the courts that know the standard of care based on child protection laws. Laws trump rules made by companies or the "water technique".
Check out
www.sportsconcussions.org for more information on preventing and treating concussions.
See
www.nationalcheersafety.com/concussionsr2pguidelines.pdf to protect your athletes