Ive had my 9002 running for about 2 months, and it just starting making micro bubbles in the tank. It also started making this girgling noise once every 10- 20 seconds, and the air valve squeals a little bit if you dont set it just right.. My water levels a half inch below the drawn water line, and i have tried closing the valve and plugging/ unplugging the unit. Please help trouble shoot, thanks