Urine smell Comes and Goes
We have a cottage in which we are getting very intermittent smells of urine (we believe). It shows up at odd times in one of our three bedrooms. Stays around for a few minutes and then after opening a window disappears. The bathrooms do not smell. I have checked the plumbing in the crawl space and the vents in the attic and can visibly see nothing. I tried lining the vent in the main bathroom to count out a leak in the wall . This did not help. All drains have "u" traps. Help!! What could it be??