Is it supposed to go on or only in cases when the power goes out??? I bought this pump and the directions are horrible!!! There isn't room for both the air stone and the check valve!! How does this stupid thing work???
Check valve designated that it lets air go in one direction and stops water from going in reverse direction. For example if your airline gets disconnected from airpump by accident and drops on floor water won't gets syphoned out frmo tank to floor. You'd be surprised how much water can end up on floor in this scenario ;-) In order to install check valve you have to cut airline somewhat in halfs and put your checkvalve between pump and airstone. Arrow shows direction in which it passes air.
