Need some advice please. See attached picture.
There is a P trap off my main drain line that is feed only by the furnace concentrate drain. This trap either keeps drying out or is being siphoned by the main drain line. It is producing a sewage smell when the trap is not full. We have a septic tank if that matters.
What can I do to ensure the P trap does not dry out? Or, should I connect it to the venting system? So it vents out of our roof, instead if in the basement.
Also, interestingly, the smell becomes stronger when we have fires in our fireplace. Maybe the flue is heating air in our attic and in therefore heating our vent system?