Unplug the pipe between house and septic tank first. Get flow of septic into the tank.
Yes that is normally the problem with a blockage
Yes, -but the tank is filling up and will soon overflow starting at the lowest toilet. Much easier to service or replace your septic pump .
The sump should work as long as you have a strainer in the shower
If it is full, you can't put more in it, full is full. Flush the toilet, it is going to come up in the shower. == == == == == ==
You have a main line blockage and or a full septic tank if you have a septic system. You need to have either your sewer line roto rootered and or your septic tank pumped if on a septic system.
There is a clog between the sink and the line to the street or septic tank. The sink is the easier path for the upstairs shower.
Broken how? As long as the drain is still connected to the tank the water will go into it. Where it goes after that depends on where and how it is broken.
form_title=Septic System Installation form_header=11023 How would you best describe this project?*= () Install new septic tank where one does not exist () Replace existing septic tank () Repair septic tank Specify the items that you already possess in your home (pick up all items that apply)*= [] Kitchen sink [] Dishwasher [] Disposal [] Bathroom sink [] Toilet [] Shower/Bath tub [] Utility sink [] Washing machine [] Pool [] Spa
Usually into a sewer pipe that goes to a water treatment plant.
You are not supposed to use any harsh chemicals when you have a septic tank. It messes up the chemical balance and the drainfield can fail and you could pollute the groundwater. http://www3.doh.wa.gov/here/materials/PDFs/24_SepTank_E04H.pdf
Check you vent stack connection inside the house. Gurgling may have been caused by a clogged vent stack not equalizing the pressure. Now that gurgling has stopped it is getting air. Start your checking there. ----HYPOTESIS The shower drain in a spare bath gurgled when the toliet flushed or the sink water drained When the shower was used it leaked to the ceiling below. Now it does not gurgle -How do we find the leak?
Look into installing a trap. In older homes fixture traps aren't always up to code and allow air to flow freely through the waste pipes.