Can someone explain how the water storage system works on the Unicorn? What is the wheeled water storage tank - is it like an Aquaroll or is it designed to be an on board tank? My Senator 5 has an onboard tank which is topped up, via an onboard pump, from the Aquaroll. Originally it was fitted with two lever valves which were under one of the seats and had to be altered to allow for filling, inside or outside tank. Mine was altered to a system of electronic valves which are controlled by a simple switch - I don't really want to go back to a manual system if I buy a Unicorn