Long-term food and water storage are no longer solely the realm of preppers who are planning to be self-sufficient for years. Those in earthquake-prone zones, as well as those who just want to be prepared for a situation that might cut off access to supplies, have long looked for ways to increase their freshwater storage in ways that won't result in them drinking plastic-flavored water if they have to use what they've stored. With the potential for coronavirus quarantines, having a long-term supply of water that is not from the tap is valuable. However, the containers need to have certain qualities.
Many large water containers, like tanks, are not meant to be stackable; the weight of the water in upper containers would handily crush the lower containers. But smaller containers might take up too much floor space if they were set side by side only. And many of these containers are big enough so that the weight of the water inside would still be too heavy for a lot of shelving. If you're looking for smaller containers, you should ask about stackability to save space.
Seams, where panels of the container were fused together, are weak points in long-term storage. Even if the container sits on its own, nothing stacked on top or poking into the base, the seam can deteriorate as the weight of the water in the container presses down (the weight of water is a factor you can't ignore because it does influence how well that storage holds up). The result is a leaking seam that wastes the water and ruins your floor. Look for containers that do not have seams on the underside of the container and that are not too close to the base. Note that the container might have multiple layers, with an exterior layer having a seam on the underside of the container, but an interior layer having no seam.
Large containers are perfect for long-term storage when you plan on staying in one place. However, there is always the possibility you'll need to evacuate. Many people rely on commercial bottles of water bought from a local store, sticking a few smaller bottles inside go-bags and backpacks. But those need to be changed out frequently to avoid having the taste of plastic seep into the water. It's easy to forget about the bottles for a couple of years. Getting a few bottles meant for long-term storage that are also portable is very helpful.
As you can see, successful long-term storage needs to use different options that give you access to water in different scenarios. You need to prevent leakage, want to prevent bad tastes from forming, and should give yourself the option to carry the storage if needed. A long-term water storage container supplier can point you in the right direction.