Incorrect venting.

Pump pits require there own dedicated vent line not shared with anything else but run directly to free air.

It has its own dedicated venting and no obvious clogs since everything drains quickly -that is what has us puzzled.

You have described something simply not possible.

The venting is shared at some point, or the pump is generating a whole lot of back presre in the drain and is not vented correctly.

If the venting was correct there could be no way to make a bubble come from a toilet with an ejection pump.

The Liberty pump station has it's own dedicated vent up from the buried tank and the main level bath vents out into attic area. The pump station and main level bathroom do share a drain line to the septic tank, with the main level bath being closer to the septic tank.

When was the last time your septic tank was pumped?

Where and how is the lift station connected to the house DWV system?

Thanks. Didn't even think about septic being full. I am not aware that it has been pumped in the 9 years I have lived here.

On septic pumping timeframes:

Here is a link that might be useful: GW post about pumping septic systems

A septic tank is always full and pumping the septic tank will have nothing to do with the problem at hand.

I just know that when my parents had trouble with sewage backing up--it was because the septic needed servicing. My thought was that if the "troubled" drains are closer to the septic tank than the other, perhaps the tank is nearing a service time.

If it hasn't been serviced in over 9 years, it is probably time to do so, regardless of whether it solves your problem or not (and if it solves the problem, BONUS!)

(Report back?)

Back for more help.

Son went away to college so downstairs bath wasn't being used. Now that he is back the bubbling has continued.

Since this posting we had septic pumped, check valve replaced and lower level venting checked.

I have noticed before I hear the ejector pump kick in to push water out, the water in the upstairs toilet slowly drains down and then there is a gush of bubble coming out as pump kicks in to push water out. There are two AAV vents in the attic. One is for the main bath area, and the another on the other side of the house above kitchen, laundry room. In the crawl space area where ejector pump is the pump has a separate vent pipe coming straight up and the vanity, toilet and shower are connected to and AAV vent.

Any other suggestions?

"I have noticed before I hear the ejector pump kick in to push water out, the water in the upstairs toilet slowly drains down and then there is a gush of bubble coming out as pump kicks in to push water out."

It still sounds like the vents for the pit and the rest of the system have become interconnected.

They are required to remain separate, all the way to separate holes in the roof.

The pits vent line must run all by itself all the way to free air.