In Romanian, they seem to talk very well in kilolitres. In English, it is valid, but just not commun. Officially in SI, a kilolitre is one cubic metre of volume anyway ...
Why can't you say 'it is a kilolitre of water' since the answer given it 'it's a kilogram of water'. In the English used where I live (England south) we don't put an apostrophe to shorten 'it has' to 'it's' do I presume this is a US English shortcut?