Hello, this is my first post. I am a happy owner of a salt pool in Phoenix AZ. My brother called me from NCal and is having his vinyl lined pool reconstructed. Are there any regulations or can anyone recommend how far below water line the return line should be? His pool is approx. 9ft deep, it currently has one return valve and the person working on his remodel has positioned it about 9" below water line. Should he have two valves? Is this deep enough with the pool only having one valve? He has one skimmer. Am I using the right terminology? Thanks for any help or advice that you can give.