My downstairs toilet bubbles when I run the washing machine. With the first load it does NOT bubble during the first drain cycle (wash step), but it does bubble during the rinse cycle and every load I wash for the remainder of the day. The cycle repeats on the next wash day. Periodically, the washing machine drain cycle will suck water out of the toilet. It is bubbling not gurgling.
There is nothing happening in the downstairs shower and sinks (including kitchen sink), or the upstairs toilet, bath, and sink. And, the water drains fine. However, I did notice that the upstairs shower did drain a little slow lately. But, I messed with the overflow cover so I am assuming this is the problem with the slow drain.
The main drain line to the septic tank is clear. It was checked via camera. However, we did notice a little water standing at the septic inlet port. The plumber suspects that the inlet port or outlet port is semi-clogged. He did not check the soil stacks because of the small amount of standing water at the septic inlet port. He said that was my problem.
The septic tank was cleaned out last year. It was basically empty, but I had just bought the house so I wanted a "marker" for the health of the septic tank.
There is one main drain line to the septic tank. The following lines tee into the main drain line: the most upstream drain line is the washing machine, next is the downstairs shower, then the sink, then the soil stack, then the toilet, then finally before going out under the house to the septic tank is the kitchen sink (including dish washer). I am not sure where the upstairs bath ties into the drain line.
My Question: Does it sound like a clogged soil stack (vent) or a septic inlet/outlet port issue?
I live in Tennessee so snow piles are not a problem. Also, I have visually checked the vent pipes on the roof and they "appear" to be clear at the outlet.