I've completely taken it apart and cleaned it and put it back together- even ran it without filter media...yet it's still doing the same thing.

Last time I only filled it half way up like suggested and when it switched itself off to expel air it did exactly that- air was coming out of the Intake pipe and water was being sucked up into the filter...however then it all came out of the filter and flooded the floor again.

I tightened the lid on as much as it could be (I used a spanner to do it).

Any other suggestions??? I'm going away tomorrow and If I can't get it fixed tonight then I'll just sell it on.