By my front door I have a manhole cover. Since yesterday there has been quite a strong smell of p*o wafting up. The bathroom is just to the left of the front door. The toilet appears to be working perfectly, no blockages or anything. Sometimes I have to flush a few times to clear the toilet of paper and the obvious but otherwise it seems okay. There is another manhole cover about 15 feet away on the driveway nearer to the road but I can't smell anything from that one. My property is detached if that makes any difference.
Any advice please?