When I built my restaurant 11 years ago, all mechanical systems, including the grease trap were up to code. Recently, my city demanded that I retrofit a much larger grease trap (1,500 gallons). I hired a contractor recommended by the city inspector and got the new trap installed. Within days after the installation, the smell of sewer gas was all over my property. Since the installation, the contractor has been back at least four times to try and fix the problem. I have resorted to calling other contractors to evaluate the installation. Their opinion is that the contractor should not have snaked the sewer lines into a giant "S" to accomodate the retrofit. They say sewer lines should run as straight as possible and be correctly graded. The problem is that since the city inspector green tagged the rough-in and approved the installation, no plumber will put anything in writing that would pit them against the inspector. Suggestions, anyone? Thanks.