Assuming all fixtures are properly vented, is there any need for a vent just before a whole house trap? I am not thrilled about having a whole house trap and may remove in the future, but current there is a open piece of pipe (pointing up) in the basement just before the whole house trap. I am not sure if it should be capped or a pop up vent or vented to the outside. Is this vent letting air in or out? (Guess I can check that with some saran wrap over if).