The building code is most likely going to require a trap to prevent gases from backing up into the house. I know they had to put them in my home.
The drain from the toilet to the main drain is plugged and the branch to the shower is not. If the main floor toilet flushes, it is between the two toilets and not between the house and the sewer.
Not directly.
By cutting in a cast iron Wye so the flow enters the sewer line (soil pipe) at a right angle
The sewer
You can get a back water valve. It is similar to a check vale/ the back water valve goes on your main sewer line out side of home. It is desined to stop black water form coming into your home if main line stops up. Thay do make a device that can be installed into an exsisting drain it lets water through your drain but will not let water back up through you shower drain.
the sewer is where things that you flush or put down the drain go, a drain is the opening is a sink or shower that sends things to the sewer
YES !!!!!!!! Minimum 2" P Trap Yes, and it needs a wye not a tee, and it needs to be vented properly.
full block of main drain. shower is lowest open area for back up to occur.
Probably not, but where does the water from the sink and shower go and what sewer problems are you having?
The drain from the toilet to the main drain is plugged and the branch to the shower is not. If the main floor toilet flushes, it is between the two toilets and not between the house and the sewer.
Heck no as it is a very carcinogenic mixture
Not directly.
One drain outlet is sufficent provided the drain outlet to the sewer line or to the gully outside has the correct gradient fall.
Most likely a drain has dried out and there is no water in the trap to stop the gas from coming up. Sink, shower, or main floor drain.
By cutting in a cast iron Wye so the flow enters the sewer line (soil pipe) at a right angle
Is there a floor drain or any other drain nearby that is not used often? Sometimes the p-trap in a drain will dry out and allow sewer gas to escape. The smell becomes more intense when hot water goes down the drain.
Do you have an upstairs tenant or the sewer is backing up.