Water Storage is much easier than food storage in that you only have one item that you are dealing with, but there are some concerns to be looked at. First what are you going to put the water in? Cases of water bottles, 2, 3 and 5 gallon store bought sealed bottles, 55 gallon drums, and hundreds to thousand gallon storage tanks. You decide on your need and ability. I’ve been advised to not reuse empty milk jugs as the plastic is too thin to survive for any length of time.
I personally carry a 5 gallon jerry can in my trunk that I change out every few years, plus several 24oz bottles in the passenger seat. I plan on getting a couple of 55 gallon drums which can be had for as little as $5 each if you know where to look. Plus I have 2 sealed, three gallon bottles in a storage site in town. I probably need to get more as soon as I can afford them.
Now, water for the most part can just sit there and be happy, but there are a couple of things you have to do to make sure it stays safe.
One- treat the water with bleach chlorine or some other disinfecting agent before storing.
Two- Have a filtration method available in case something gets into your storage.
Three- If you are still not sure, boil it.
Four- Don’t store the majority of your water supplies near your food supplies or near any type of sanitization concern i.e.; out houses, where you clean carcasses, water courses like rivers.