We have a shower drain that has been draining slow for about a week now. Yesterday I noticed a sewage smell coming from that drain. The shower had NOT recently been used. We live in the city of Appleton. Any ideas on what it might be?? Also yesterday I poured a drain cleaner down the drain (twice according to directions) and the odor seems to be getting worse. The drain cleaner helped the water drain a little faster but the water still backs up in the bottom of the shower. The water appears clear.