Occasionally we get a strong sewer odor outside, after observing wind patterns it appears to be when the wind is slight from the W. Out lot is 1/2 acre with a box effect on 3 sides. We are wondering if the odor is coming from our roof vents/stacks, OR if we are getting it from surrounding properties? We are having a hard time pinpointing the problem. It comes and goes based upon wind patterns, although we notice it every day. The odor is stronger at times, and we're wondering if when the wind blows slightly from the W if the odors are being trapped by our lot design? Plumbing outfits here locally have not heard of any type of filter or method of fixing this problem, which brings me to you. We appreciate any light you can shed on t his. Look forward to hearing from you. Best Regards Vicki