The ball bearing is not done yet! If you have a multi-hose hookah, you know that only one person can smoke from it at a time. The other hoses must be plugged by the other users in order to allow the smoker an effective draw - that is, unless you have the majestic auto-seal!
Auto-seal is a feature on many modern day water pipes, such as the Mya Saray hookah, which allows air to be drawn from the hose but does not let air back in, which means that you don’t need to plug the extra hoses with your finger when someone else wants to draw. Inside the hose port there will be a small ball bearing that works very similarly to the purge valve. There is always a screw or a plate above the bearing to prevent it from being sucked into the hose while still allowing airflow.