Septic Tank Smell - Interior
I'm new here and have been trying to figure out my plumbing issue for a while now. We just moved into a new (100 year old) house with a septic system. It's my first experience with a septic system so please bear with me.
We had it pumped 3 months ago when we moved in, but there is still a septic gas smell in the back room whenever the bathroom or kitchen taps are running, or when we flush the toilet or do laundry (Basically whenever water is draining out.)
The house is small -1000SF slab on grade foundation with a VERY tight (12" or less high) crawlspace area underneath the laundry room/bath area. We can see the drain pipes from the laundry room run into the floor and the vent stack is nearby on the exterior wall enclosed in an unheated shed attached the back of the house.
I tried running the hose into the vent stack to unclog it but that did nothing for the smell. The bathtub and sinks have no problem draining, no gurgling, they just cause that disgusting smell to come out near the laundry room (now renamed the poop room) drain pipes.
The washing machine looks very new and there is no visible mold inside, so I'm pretty sure this is a venting issue but I'm not sure how to fix it as the pipes are under the floor and hard to access without ripping up the current floor which I'd like to avoid if possible. I've read about small air-intake vents that can be attached to the drain pipes to help vent but I'm not sure if this will work in this case.
Any advice? Thanks!