If you really what to figure out water usage for your shower get a gallon bucket or larger and time it how long it takes to fill it up and that well help you calculate how long you can take a few showers based on your usage On my Toy Hauler at two minute shower uses 3 gallons of water my wife times hers, she'll take a four minute shower but on our last day of dry camping we don't care as long as there's a little to flush the toilet. Rinse off, soap up, rinse off. You'll most likely never fill up you black tank or even come close to it. You can dump you gray water depending where you are. Note: If water comes up in your shower you gray take is FULL!!
