The "delayed" gurgle

[MontanaHeaven]

RV: Paradigm 310RL. The last couple times I've dumped one of my grey tanks I hear it begin to run for a few seconds, then there's a brief pause of a few seconds, then a bunch of gurgling/bubbling and then the rest of the tank contents rushes out. Normal?

 

[Whitewolf]

Hmmm. The only time I've experienced this is at a campground that their system wasn't properly vented.