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????

BasementGuy

If the plumbing isn't being used often the traps can dry out...I have also seen the vents freeze over (if you are in cold climates)...Or maybe you have critters.

N0help4u

Were there previous owners that may have had a potty training age kid or something?
What kind of flooring do you have?
When I moved into one of the houses I used to live in you could smell cat pee every now and then like you are saying. It was in the wood floor by the sliding glass door. I used some pet odor & stain remover spray. It works for other odors to.
Carpeting will hold in smells also.

hagerfireworks

We had a sick cat and a urine problem. It was cleaned up
well but when the humity is high and temp. is just right
we still get a wiff of it. If you have high humity this might
be the problem.