Maca

Hi. I have a Mspa Tekapo inflatble hot tub. I would like to store and drain it over winter. I have emptied the tub of water and let the bubbles/jets run for 20 minutes to clear water from the system, however when I move the tub around there is still water sloshing about it. It sounds like a considerable amount, but I'm not sure where this water is stuck. Can anyone help me how I can drain the tub fully. I can't do so with the water currently inside it. Thank you.