We have the 645, so might be a slightly different layout. Do you know how to drain your system? As you walk into your caravan, under the seat opposite you should have the two taps, they have to be both in the same position, facing downwards, for water to be pumped in from your aqua roll. There should be a yellow lever also under that seat, which is a drain valve - this needs to be in upright position (or as you pump water in, it will pour straight out - as we have found on several occasions). When you press the water button on your display panel (ours is over the door) it should tell you how much is in your tank.
Once tank is full,(40 litres, so should take one full aqua roll), (if over full you will hear it coming out under front of van).
Once its full, then turn both taps to the right, and you will hear the pump slow down and cut out.
Then refill your aqua roll, and as you use water, it will automatically pump refill into the van's system. Even better is on a fully serviced site, where you can buy Aqua source hose, which just connects onto the tap on your pitch directly into your Whale pump, and you leave it switched on, and you have constant running water.
We have got two aqua rolls and keep both filled up, so there is always enough to refill the tank, and keep topped up for showers, washing up etc.
Hope this helps - we find it brilliant.
Cheers,
Rich