We have a double kitchen sink, connected to a dishwasher. Our a/c unit also drains into the line from the attic. There is a vent on the roof. Everything was installed 6 years ago during a remodel. The sinks have been running slow recently and are now gurgling. We removed the trap and there was nothing there. We ran a garden hose through the line and it did not back up. We had the septic cleaned. What is our next option?