If the cylinder is sealed (which I guess it must be if it's lying on its side and still has the same volume of water in it)....what difference does it make how much is in it? Why do we care (we can't do anything about it)?
The reason we care is that the cylinder contains the rainwater that is used to flush my loos and wash my clothes. Thus I would like to have a rough idea at what depth of water I should set my system to add mains water so that I dont end up leaving a huge floater in the loo.
