I recently bought a house that has a finished basement. The shower doesn't have a trap but we keep it covered. The house is always filled with the smell of sewer gas. I have one drain that is half exposed and half under a carpet. Should I pull back my carpet and cover that drian? Is it possbile that there could be a second drain? (Its a large room)If so how do I find it without ripping up all of my carpet, and what should I use to cover it with? Is it possbile that the smell is coming from somewhere else?