I am having an issue with my hot tub. I manage several pools at a hotel, and have multiple hot tubs. When the air blower is turned off there is still air getting shot out of the return jets. When the blower is off, I closed the return valve for the air line, and the bubbles stop, so I know its not a suction leak on the filter system. I can feel slight suction on the intake of the air blower pipes. There is also no power going to the blower when the timer is turned off. I have an Ametek DR505AW58M spa blower. Anyone have any ideas on what is causing the air suction when the blower is off?