Portable Water Bag For Gray Water Treatment

I am interested in a bag for a gray water treatment.

I am thinking of a water bag (not a tank) because I would like to put it under the deck at my cabin. How resistant to weather are they? In the winter it gets very cold here but no one will using the cabin at that time.

The cabin will have anywhere from 4 to 10 people staying in it at one time. The price for the water bag will be a consideration as well.

I am thinking of placing the water storage bag under a deck which will have 4 foot clearance, enclosed on 3 sides. I am able to make any necessary changes to how it is enclosed.

It just occurred to me that a bag for fresh drinking water would be good as well if there is a bag for such an application. If I decide to make a purchase I will provide you with that info at that time.

I have the room for something fairly large I would think. Is bigger better? Obviously more storage. Are there any negative concerns?

Please let me know.