Obviously, when you fill a jug of water for storage, the water needs to start as pure and clean as possible. Secondly, the jug needs to have been rinsed in a dilute bleach water solution (very dilute) right before filling.
Next, the jug needs to be filled until it overflows – So as close to the top as possible. The lid should be dipped into a very dilute bleach solution and placed on the jug. This should inhibit much of the bacteria from developing from a dirty jug or airspace inside. To get water storage solutions, visit https://www.kliptank.com/.
The last hurdle was the purity of our water. I wasn't comfortable with the amount of sediment, minerals, or possibly bacteria that was lurking inside. While boiling is safe to purify water for immediate consumption, storing boiled water in another container can re-contaminate and start to grow bacteria as we found several times previously.
Finally, we added a small amount of diluted bleach water to our jug and rinsed it well. We took a gallon zip-lock bag and added a very dilute bleach solution to that and dipped the lid before placing it on the water container. We took the jug to the local market and filled it at the Culligan water station.
It was only $2.00 to fill 7 gallons! We filled the jug to the brim, even letting it flow over just a bit, then we re-dipped the cap into the zip-lock of dilute bleach water and placed it immediately onto the jug, inhibiting bacterial growth in the top of the water container.