Couple of questions: Are you on bore water? Do you have a septic tank? Is your plumbing properly installed?

Just asking, as at our last house we owned the drain from the bathroom basin did not connect to the main drain by 1 inch. So all the water was just pooling under the house and smelling. Where we are at now we have both bore water and septic tank. The bore water has gotten a bacteria in it and is smells rank, so when we use that water we get a yuckky bad drain smell. If you have a septic, then it may need to be emptied.