Two-story home on septic (bought it 3 yrs ago.) Built on slab in Florida, so can't access plumbing - no basement. 1st toilet bubbled when the washer (also 1st floor) drained recently. Problem seems to be getting worse; now 1st floor toilet bubbles when 2nd floor toilet is flushed, too. The toilet bubbles, drains, then doesn't refill until flushed. With little money and panicked, I'm not sure whether to call a plumber, call a septic pumping company, or whether to somehow (?) locate the main line cleanout buried underground outside and rent a snake. Who should I call? How can I tell if this is a septic problem (full) or clog in the line?