hi - This is pretty weird but --- when I sit on my toilet and then move my rear a little off center so my butt is not making a seal in the back there is a hissing sound as if air is escaping - not from me but from the toilet bowl. I tried shutting the lid to see if it made the sound when I lifted it back up and it did not. It just started to make this noise. What's going on here?

 

does your bowl rock back and forth at all? If so, perhaps your toilet is coming loose and when you "adjust", the toilet is rocking to the side causing it to actually slightly leak which might not happen without your weight on the bowl. I'm only a member and not a really good plumber yet, but I would think that they might suggest that you need to replace the wax ring and tighten your bowl down.

 

the lady, Welcome to the DIY Forums.
30 years as a Plumber and have never heard that one. Lets start with what I DO know. Toilet seats have little rubber or plastic "feet" on the bottom side so that if the seat is dropped, it doesn't break the bowl. This also prevents a "seal" when sitting on it. Please tell me that you have one of those "comfortable" cushioned seats. Then it could be a slight crack in the covering that allows air to escape as you "move off center". I am hoping I have solved your problem but if not, PLEASE reply back when you do find it. I just have to know the "end" results of this. Good luck.

 

The bowl is pretty stable - I can't get it to rock. The toilet seat is oak. The air is coming from inside the toilet as far as I can tell.

 

Do you by any chance notice that the water is lower than usual when this happens? Could anyone else in the house be using water at the same time you feel the air? This could be a clogged vent that is allowing the water in the toilet trap to be sucked out. This would give you the sound of air moving.This could also happen if you live in a multi family dweling that has another bathroom directly behind yours. The vents may be tied together.

One last thought, is the tank securly fastened? If you lean back against it does it move slightly? If it moves it may be allowing the ball/float to rock and allow the fill valve to allow water into the tank. This would happen in short bursts that could sound like air hissing. You could test this sound by removing the tank lid and pressing slightly on the ball/float and releasing it quickly. is this the sound you hear?

Please keep us informed on what you find. Other than the suggestions above, I am somewhat baffled as to what could be causing the sound.
Good luck

 

I have the same thing just happen to two of my toilets within a weeks time so I'm beginning to think it has to do with the water pressure or something other than the individual toilet. I have little screws on the top of the valves I can adjust but I'm going with the theory that it is not the toilet itself.