When the shower is on, sewer smell comes up from the drain. I can't figure it out! Clues:
- It only happens when the water is running.
- No other drains (bathtub, sinks) in same room or elsewhere do this.
- It's a rural home with septic system, about ten years old.
- For years, the shower was very low flow but when I got here, I fixed the flow (a defective washer was plugging the shower head supply hose) and I think that's when the smell started.
- The shower drain pipe goes straight down for about 7 feet, then there is a trap, then a horizontal run where it joins other drains on the way out.