Originally Posted by
snare5117
Interesting. Our onboard crew said that people should be able to use the bathrooms once we were in the air, but would have to use bottled water to make them flush. No idea how that's supposed to work; I didn't use them myself.
PHL to LAX is a heck of a long run without working water. At least this morning's flight was only a couple of hours.
Under 16k feet there's a vacuum pump that creates the suction to empty the toilet bowl. Above that differential pressure is used to create the vacuum. If the pump wasn't working that would explain why the lavs wouldn't work on the ground. Kinda surprised that they could dispatch the plane if the pump was inop.
There's a great YT channel by an AA mechanic based at LAX, Stig Aviation, that actually went over how the lavs work in a recent video. The segment starts around the 31 minute mark.