our schoolie will be used for winter travel almost exclusively - we won't worry about grey or dark tanks, or even fresh water tanks - we'll pack our water in 5 gal ( 20 litre ) pails - a five gal pail and a scoop is the most efficient way when watering or feeding 20-odd sleddogs - if the floor of the bus is freezing, the 5 gal pails can be moved to higher ground ( a counter top ) so it doesn't freeze - same method for cooking or washing up, scoop water into a pot and heat it up for washing ) and a porta-potty or chemical toilet for those 'spending time alone' moments - at 40 below, there is little under the bus that won't freeze, so NOT having the convenience of indoor plumbing will be a lot more convenient than having it - I have old trailers, even an old motorhome (has a big dodge motor ( 440? ) with 58,000 miles on propane, complete with push button transmission if anyone is interested ) that have sinks, counters, cupboards, stove tops burners and ovens, propane furnaces with circulating fans, lots of 12v light fixtures, pretty much everything we need except bunk beds and mattresses that aren't mildewed - add an efficiently burning wood stove and we'll have a shelter every bit as good as a log cabin off grid in the woods - ( I can smell the cowboy coffee being brewed on the wood stove as I write - best coffee ever made - lol