I've running a Polaris 280 cleaner and just got a new booster pump for it (PB4-60 Zodiac). Running my main pump at 2k RPM during the daily Polaris cycle. Just noticed this for the first time, but there is a intermittent high pitched whining noise (pressurized air) at the connection of the Polaris hose. I also see high pressure bubbles getting pushed out where that little black cap is located (see picture). Is this normal operation and that connection is made to be an air release or do I need to replace some parts to eliminate an air leak?