All the water served for drinking, cooking, veg prep in the restaurants at Desire comes from large 5 Gal bottles(fully treated from an outside supplier) which are delivered daily. All Ice for the bars is also made from the same fully treated bottled water.
There is bottled water delivered to your rooms mini fridge every day and also available around the resort
The tap water in the rooms is filtered in the onsite water treatment plant - however I would suggest that you only use the bottled water for drinking and brushing and rinsing your teeth.