Something strange here.... After having my septic tank pumped out, I am noticing some strange odor coming from the shower. We had it pumped about 3 weeks ago, now we smell a mildew type dank odor coming from the walk-in shower drain.
mysticokra hit on a good point about whether the vent is clogged. Check to exit point on the roof to make sure a bird didn't build a nest there to stop the flow. gurgling and smell could indicate a clogged vent.