Water being sucked out of toilet bowl?

[newmex999]

Is there anything else besides a clog in the main line that then suddenly opens up that would cause the water in the bowl part of the toilet to be sucked out allowing sewer gas in the house? This has happened twice in the past 2 weeks. The first time all the water in the bowl was gone(this is a newer model toilet that has very little water in the bowl to begin with and has been installed for 1 year) and just today where it sucked about half of it out. This toilet is the one closest to where the main line exits the house.

I am on a septic system and last time this happened I opened up both cleanouts in the main line and the water appeared to be flowing freely into the septic tank.

I know the vent stack has a screen over it, and is topped by a 180 degree elbow so the screened portion is pointing down towards the roof(so that nothing can settle on the screen to block it)

Also, if this was an internal leak in the toilet, wouldn't this happen consistently?

 

[LLigetfa]

Have you tried to plunge the toilet?

 

[Sponsor]

 

[Jadnashua]

Depending on how long between uses, if you happen to flush dental floss, and it gets stuck, it can act like a wick. Is this bathroom back-to-back with another? If so, and you don't have the proper fitting in the wall, flushing one could cause the other to get suctioned out. Older, high flow toilets flush slower, and may not present the same problems with the incorrect fitting.

 

[hj]

A main line "obstruction" can also suck the water out of the bowl as the water slowly dissipates. In other words, ANYTHING that causes the main line to fill with water, regardless of HOW FAST it empties, can cause your symptom.