Sewer Smell

I came across this site looking for answers to this terrible smell coming into my house. A couple of months ago we had to have a new leech bed put in because our septic tank had filled into our old one without us knowing. Since we had the new bed put in we have a terrible sewer smell coming into out house but only when we drain our bathtub or use our wash machine. The smell is really strong in my master bathroom in the closet and the laundry room. On the side of the closet behind the wall is the vent to the roof of the house. The laundry room is located on the other side of the bathroom closet. The odor is really bad on our back deck beside the vent also. Is it possible the septic could have backed up into the vent maybe?? I have no clue to what it might be. All our pipes have been checked under the house and the ones starting out of the house to the new leech bed are all new and made sure to be right. Any help would be greatly appreciated. Everyone we have asked about this problem say they don't know what it could be. Some say the pipe may be stopped up and needs cleaned but how would you clean it?? Others say it can't be stopped up. Thank you very much in advance for any advice.

(not a pro)

If it only happens when you're running some of your fixtures, I'd think it had to do with water being siphoned out of other traps, leaving them open to pass sewer gasses.

Water would only be siphoned if your venting wasn't working properly. I know it is possible to declog your vents, but defer to the pros to tell you how.

To that end, I believe the purpose of the vents is to discharge toxic sewer gasses far enough away from where you can smell them. That's why they're supposed to go through the roof, or far enough away from openings on the side wall. I wonder, therefore, if the vent by the deck should be re-routed in addition. Pros?

Thanks

Thank you for the reply.