Plumbing problem; when I run the water in the shower,lavatory or kitchen sink for 3 or 4 minutes or longer?

I hear a loud gurgling sound coming from the toilet. It does this often but not all the time. It has been suggested that it's probably a vent problem, but the vents seem to be clear, both of them, the one that comes out of the bathroom and the one that comes out of the kitchen. I am puzzeled to why it is doing this.

Public Comments

1. its the vents...you cant see them because they are behind the walls, but thats what causes your problem....
2. The vents come through the roof and I don't think your looking at them, you wouldn't be able to "see" them to tell if they're clear. A plumber would run a hose or snake down them to the toilet or sink to clear it. The second problem would be a full septic tank if your rural or a plugged line that's not letting the water flush all at once.
3. If the vents are not blocked, then the problem is that the shower, lavatory and sink are not properly vented. Each fixture should be vented. The vent connection to the fixtures should be within 5 feet of the trap. And the 5 feet is installed pipe length, not horizontal distance. The vents from the individual fixtures can then be connected to the main vent that goes to the outside of the building. If you cannot connect any vent piping for the fixtures, you might want to look at using air admittance valves. I would have the system checked by a licensed plumber.