From our personal experience, we consume about 1m³ house hold water per week. On a houseboat, you can chose having no tank at all, multiple parallel connected tanks or one big tank. You can also consider collecting rain water or filtering water from the canal/river. The used water is called gray/black water and cannot always be dumped just like that in the canal or river.
No water tank:
this works in the cities where you have water from the shore; whenever you want to move, don’t count on it you will find water elsewhere.
multiple parallel water tanks:
very cheap to find are the 1m³ plastic tanks which you can put in parallel; disadvantage is that these tanks are not designed to last a lifetime and might leak; especially at the connections.
single big water tank:
has its extra price, but one big heavy-duty tank will last more than a life time.
Collecting rain water:
can be collected from the sidewalks: filters to be installed and cleaned very regulary rain water
can be collected from the room à ok, filters to be installed and cleaned regulary
is ok for washing machines and toilet; be carefull for bad, showers and kitchen because of salmonella
Filtering water from the canal/river
via filtering/UV, water can be taken from the canal; seems this works quite well on rivers/canals with not too much dirt in the water. Beware that you will not pay the price double by electricity consumption and replacing filters.
When bunkering water, a pump (hydrophore) is needed to distribute the water under pressure to every water-tap. This hydrophore can be either 230VAC shore or generator powered or 24VDC battery powered.
To bunker the tanks,
you could ask the firemen; this has a significant cost because of the man (and truck)hours, but is minimum personal effort
you can navigate the boat to the nearby ship-bunker-facility.
you can drive trailer with 1m³ from a friend neighbor who is ok to provide you the water (at a cost).
you have a personally water connection on the shore
Below, you see the blue water tanks from our ‘Lucie’: 2x 1500l rainwater for in front & 1x 5000l freshwater for in the rear.
Gray/black water
Gray water is waste water not from the toilet (e.g. bad, washing machine, kitchen) while black water is waste water from the toilet. At time of writing, I did not exactly checked the current obligations, but I remember like:
gray water is ok to be dumped directly in the river/canal
black water can only be dumpted directly in the canal by professional cargo-boats and seems to be still tolerated for older houseboats who do not have a black-water tank installed yet.
black water should be collected in a black-water tank and emptied as a septic tank; not fully clear if septic tank overflow is allowed directly in the river/canal.
Certainly future proof to invest in a water-cleaning system where a first (septic) tank flows over in a second (aerobe bacterial cleaning) thanks that flows over in the river/canal.
Below, you see the black-water tanks from our ‘Lucie’ dimensioned on a family of 4persons, a first stage tank and a second stage tank going around the central 5000l drink water tank.
To evacuate the water, we could benefit the natural flow because the ship is naturally inclined backwards. We centralize this drain to the right side of the ship and once it reaches the tanks, it is mixed and pushed up by a dedicated pump in the first stage tank. Then, a natural flow goes over from the first stage tank to the second stage tank. Then, a natural flow goes over from the second stage tank to the outside. This exit is via a pipe welded to the side of the side and has a valve to close this. Mandatory for ship certification!