We moved into this house a little over a month ago, we are renting to own it. It's a 1998 doublewide that has been remodeled, we are on our own septic tank and it was emptied long before we moved in.

A few weeks back I was trying to take a bath and noticed a sewer smell coming from the tub, it seemed to be coming from the faucet but not the water itself. Then it started coming from the bathroom sink drain and the toilet. It comes and goes shortly after we run any of the water in the bathroom or flush the toilet. A retired plumber told us he believed it was the roof vents, we have two. One for the tub and one for the sink and toilet. He told us to run water down them and wait to see if we heard any whoosh sound which would be a blockage passing through. We did this and heard the whoosh sound out of the vent for the toilet/sink. Nothing to be heard from the other one. We thought we were good to go, problem solved. Nope that only lasted a few hours and then got worse. The smell still only happens if the water is running/after its been ran but the smell is worse. And I don't know if it's related but after we did the roof thing the cold water in the tub has almost completely stopped working. Its only a drizzle but you can hear pressure behind it like it's trying but is blocked.

I've called the man we're buying the house from but only got his voicemail, which i figured given that it's father's day weekend. But this smell when it does happen is getting extremely unbearable to deal with and we're at our wits end. The other cold water in the bathroom is running perfectly so I dont know what is going on with the tub. Does anyone know what could be going on? And yes we have tried running water down the drains, it hasnt stopped the smell. (Its not sulfur either, I grew up with sulfur water and this isn't that. This is definitely a sewer smell).