County water house is over 50 but septic lines extended 30 years ago. Had septic tank cleaned due to slow drainage. Person that did septic tank said he removed a clog from one of the pipes. Since having septic tank cleaned we have had a sewage smell that would work its way through the house. The smell is worse when we flush. We can also smell the odor coming from the kitchen sink but not the bathroom sinks. 2 bathrooms and one of them is where the clog was. We have tried liquid plumber and put the septic enzymes down the commodes. What are we missing? We also did a lemon, baking soda salt and hot water trick I found on line. Nothing has worked.

I had the same issue a few months ago I was away from our house for a while when I came back the smell was coming in the pipes and sinks. Had the septic cleaned out and seemed OK for a few days as time past the smell got worse and came back twice as bad. Then one day out of the blue the septic back flowed into the shower the toilet and all over the laundry floor, can you hear disgusting and panic. I did all the remedies you tried before this happened and found out later there was a root in the pipe. So far so good since the snaking of the pipes but there is one other area check if you have a grease trap from your sink, it could also be doing the lovely odour I had no idea I had one till the plumber told me and warned me about maintenance of it I thought it was a drain on the veranda.

Ave you checked all the traps, including the floor drain? Where is the smell the worst? Is there any gurgling or bubbling when you flush? Back to you. Tom

I found the what was causing the smell. My first bathroom, which is used daily, has an issue with keeping water in the pipe where it is bent. I do not know if replacing it will take care of it but I will try that first. I wash my hand a lot in there and thought the water was staying in it. I will let you know. Mom said every once in a while she thought she heard a gurgle but could not find where it was coming from. The smell happened everyday but the gurgle only every once in a while from what she said.

an issue with keeping water in the pipe where it is bent. That bent pipe's called a trap for a reason. It traps the smell.

Mom said every once in a while she thought she heard a gurgle BINGO! We have a winner! The noise Mom heard was suction from a blocked vent pulling water out of a trap and letting the smell get bye,
The solution would be to snake the lavatory roof vent. Put out enough snake to reach the base and 15 feet more. Good luck, Tom