It could be insufficient venting. The water going the drain from the toilet sucks air behind it. There should be a vent going up through the roof which lets air into the drain stack pipe. If it can't get enough air, it can suck air through another drain trap. It could be a design problem, or the vent could be clogged with ice or debris.
either the vert is plugged and there is no air getting through or there is no vent at all
In order for water to flow down a pipe, there must be a vent to allow the air to escape. Above a toilet, on the roof, there is usually a pipe or a vent hood, which is connected to the drain pipe. When the toilet is flushed, the sound of water draining can be heard issuing from this vent. In addition to the above answer, the air rushing through the water may be the cause of the gurgling sound, which is the air escaping through the vent to prevent the build up of air pressure inside your water system.
When a basin drains and causes gurgling sounds in other basins -- or the toilet, in this case -- it is usually a sign that a vent pipe is clogged or obstructed. The air being displaced in the drain pipe of the bathtub has nowhere to go if the vent is clogged and is being forced up through other drain pipes.
NO.
I do not know if popcorn can be flushed down the toilet. So, I wouldn't try it.- Ashton Smith
Then unblock it UNLESS you like gurgling sounds
This indicates that it has a toilet, sink and a shower but no bathtub. A 1.50 indicates that it has a toilet, sink but no shower or bathtub.
The sewer
This is not a venting problem. You have a possible blockage. Get a plumber to check your sewer lines. They may need to be cleaned out.
Depends on if it needed to be flushed or not.
Bad venting
Water and waste