Just wondering what this is? Some sort of relief valve? is it possible that this could be contributing to the excessive air in my water system? I noticed the white spout off the side of it sucks air when the pump is filling the tank. Wasn’t sure why? I have an air problem. When you turn on the faucets anywhere in the house or when the toilet is filling all you can hear is air, And the water spits out. It comes around eventually by itself but always comes back after a few minutes. But If I bleed the lines it stays good for about 3-4 days amd then it starts all over again. I have a fibre glass tank. Are they usually bladderless? Someone once told me that. Or do they typically have a bladder like a steel tank? Thanks for any responses