I have most bits of information for fridge, Zig unit,but I have no information at all regarding the Fresh water tank,

What I want to know is, How do I clean it out ? and does anyone know how much it is likely to hold .
It is an inboard tank with an external lockable filler, it is not underslung like a westy.
If you can help, please let me know,,,,,,,,
Thanks for your time,
Fritz,,,,,,,,,,,
