[MVPerk]

I thought I would ask here as I have had no success elsewhere. My problem is this: sewer gas smell in the basement on and off for YEARS. Haven't addressed it in the past, but now concerned since we recently finished the basement. The smell was present prior to our finishing the basement and was present during the framing of it. I've done extensive research and reading of causes and cures. So far, I 've made sure all traps have water, recently hired a smoke test - which ruled out any leaks in the pipes, I looked on the roof in my vent stack, but nothing visibly clogging. The smell gets worse whenever the laundry is done, sun is out in the morning, it is windy or raining... Basically, there is no concrete reason I can find why it comes. I do know it is always in the basement and when it is really bad, it travels up to the main floor. If the wind, sun, rain are causing this, what can I do? I am on a septic, with a walkout basement, 3.5 baths with 2 vent stacks on my roof. My septic tank is about 8 feet from my house. Is there a way to vent the septic tank and would that help? Just looking for some more advice. I cannot stand not knowing where it is coming from or how to relieve it.