Abstract: A tank venting, pressure and temperature relieving, and spill preventing valve for fuel tanks. The valve has a spin chamber, having generally circular cross sections and at least one side wall inlet opening that is tangentially directed with respect to the circumferences of the cross sections. There is a circular outlet at a normally upper and open end of the chamber. The chamber cross sections decrease in diameter upwardly of the inlet opening to below the outlet opening whereby gas venting through the chamber spins a light weight, bouyant ball around the chamber so as to prevent the ball from closing during venting. The ball valve is adapted to be lifted to seat on the outlet to close it when liquid enters the chamber to a predetermined level. A heavy ball in the chamber holds the light weight valve ball on the seat when the chamber has been tilted a predetermined amount.