check or have a plumber check p trap in drain line under shower. if leaking [losing water] it wont stop sewer gas from coming up the drain. probably the most likely cause.
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. == == == == == ==
Bad shower valve.
you don't clean it in the bathtub, that will cause it to rust
You should purge all your water pipes of built in sediment. Don't forget, you are drinking the water too!
It is not recommended to use Drano with a septic system as it can harm the beneficial bacteria in the system and cause damage to the septic tank.
Almost all codes now use reference to a 1/4" per foot fall in sewer and septic lines. Too little fall will not float sewage out and cause clogs. Too much fall will also rush water out and not remove sewage properly. 2.5" per 10' stick.
septic teeth
No, it is not safe to use Drano with a septic system as it can harm the beneficial bacteria in the system and cause damage to the septic tank and drain field.
In some cases, bacteremia leads to septic shock, a potentially life-threatening condition
Sodium carbonate can safely be used in septic tanks. Many people use it to deodorize the drains in their home. It does not cause problems with the septic system.
You need to get it cleaned out.
Drano is not effective for unclogging septic tanks. It can harm the beneficial bacteria in the tank and cause damage to the system. It is recommended to use septic-safe products or consult a professional for septic tank maintenance.