Storing lots of rainwater in a flexible/collapsible container/tank/bag

Ah everything on Permies feels like home!  I've gleaned much from it over the years but this is my first post...

We are looking to meet all our water needs (drinking, household, garden) from rain that is very plentiful in our winters but sparse in our summers.  Our little house is on posts on a rock slope -- high above the ground on the south side, ground level on the north house.  Underneath the house is closed in  somewhat on the sides with wood walls and much of this crawl space is not very useful for storage, being low height and hard to reach on uneven exposed rock. My ideal is literally to store the rainwater in bag-like tanks in these parts of the crawl space.  They would lie on the rock and fill up that unused space, or so I imagine. Even though we do have space under the deck for big tanks, we are a pretty long ways up a steep narrow trail on a rocky slope from the road, and getting big heavy water tanks up there would be a very big deal.  And we would like to use the space under the deck for storage and a workshop.  And I imagine darkness is best for most rainwater storage containers to avoid UV breakdown or algae growth.  Also I think flexible storage containers could be cheaper.

Googling keywords like rainwater storage bag, collapsible water tank, etc brings up seemingly many suitable products, but info about purchasing them is not so obvious.  But before I try harder to find that info, does anyone have an experience with this sort of thing?  Or any thoughts to share?  TIA!

No experience to share, but the search phrase you're looking for is "Bladder tank" You'll do a lot better searching for that...


Here's some up to 25,000 gallons

https://store.interstateproducts.com/products/Water-Tanks?gclid=Cj0KCQjw-af6BRC5ARIsAALPIlUZRPPIcxK0rvKRQZSohptWbarJ-3LaBpgWIn-1XYSo-iZfFtQwGTMaAtL6EALw_wcB

Yes its a viable method to store water./
You would need to consider using a number so each can fill properly.
Can you share any photos please?
Bladder tanks is the term we use in Australia.
Freezing may be an issue, but the rocks base may be enough to help prevent it.

Bladder water storage

Viable, definitely.  Cost effective, maybe.  The bladder tanks need to be set on level ground or they roll downhill.  They need a sand base to protect from sharp rocks.  They are still awkward and heavy to move.  And cost a lot more than a poly tank per gallon of storage, unless you find a deal.  There were military surplus ones out there, but I haven't seen them lately.

I'm an anti plastic kinda person don't use it unless you absolutely have to. your water will leach the chemicals in the plastics. you might consider bricks, blocks, rocks, clay, hydraulic cement, that kinda stuff can be formed  in infinite shapes. here on the edge of the smokies spring boxes are very common, they are like miniature swimming pools built at base of a hill with pipe running down mountain from a spring to keep it filled. in many places in the world for 1000's of years cisterns were used in natural rock formations bolstered by clay and other natural building resources.