without consulting the books, the basic principle is to :
1. use diff press above 16000ft to 'push', or 'blow', the poo from the bowl down to the waste tank, then separate the poo (waste) at the tank, and discharge the stinky air overboard via an orifice we called 'the poo chute', typically on the left hand side at the back - the orifice with brown streaks coming from it (insert spewing face here)
2. use the 'blower' to create a vacuum below 16000ft to 'suck' the waste down to the tank, then separate the poo (waste) at the tank, and discharge the stinky air overboard via an orifice we called 'the poo chute', typically on the left hand side at the back - the orifice with brown streaks coming from it (insert spewing face here)
The outflow valve has nothing directly to do with water/waste management.
The pressure sensor for the ovhd pnl cab diff press is, from memory and dont quote me, on the back of the gauge itself. If not, its in the equip centre somewhere.
It is possible that the cab diff press sensor can sense the subtle cabin pressure change due to toilet flush (an induced pressure leak). I would have thought, that the flush would cause the needle to dip to a lower pressure momentarily, however, there might be a phenomena/characteristic that im forgetting that causes a sudden rise in pressure when the flush valve changes state from closed to open.
hope this helps... i dont like to make over complicated explanations