Previously, you read that we have fresh (tap/rain/canal) water in our blue tanks and black/grey water in our black tanks. Now the question is how the fresh water gets out of the blue tanks in the used water gets into the black tanks.
To get the water from the blue tanks, you need a hydrophore. Reasonable priced are the 230VAC ones; expensive are the 24VDC ones. These hydrophores are silent as long no water is demanded; as soon water is demanded, they start pumping.
We have on Lucie one hydrophore to get the rain water distributed (to the toilet and the washing machines) and another hydrophore to get the tap water distributed (to the bathroom and the kitchen and hte shippershouse).
In case we are out of rainwater or in case the lady of the house wishes to wash with pure tap water, we can put the whole system on tap water by means of a manual selection crane. This crane is loated in the laundry room in the middle of the ship.
The evacuate the water:
water from the shippershouse (kitchen, shower, toilet, sink) will naturally flow into the black tank (underneath the shippershouse).
water from the main house in the cargo will naturally flow to black base where a pump will push it up into the black tank. We use the typical inclination of the ship, having the back deeper in the water than the front. We exaggerate a bit the inclination (for in case the ship would be loaded in the front) and use this as much as possible to collect al the water upto the pump. Take care not to run to far; the middle of the ship 15 - 20m is far enough. Going further will risk more blockings or the need of an intermediate pump system.
Toilet waiting to be connected:
As you can imagine, if this pump is not working, water will try to escape everywhere it can and first at the lowest places, like the shower, then the bath and then the sinks. Because of the dramatic effect when water cannot be evacuated; our pump has an acoustic alarm when loosing power or being in fault (not able to pump). Sanicubic type, quite expensive but central and effective.
Unfortunatly, we do not always hear the acoustic alarm or it even just turns itself off without giving any alarm. We learned to detect it and recover it (hear the water bubbling; push manual button when alarm is given; repower when no alarm is given).
Small boats might have a simplified system like an electric pump / grinder per evacuation place. or even a handpump.