man...seems like we have the same problems....lol try this.... keep the valves open and unplug the fx5. let the water drain in and the bubbles drain out. plug it back in. that might work. fx5 is suppose to prime itslef but everynow and then it doesnt. always happens after a water change when i forget to shut off a valve. the water flow would still be the same but made noise. so i just unplugged and plugged it back in.... thats my experience... GL