A closed restaurant loses more in a day than the tank costs.
Birmingham water is reliable. It is not infallible. A boil-water notice closes a kitchen, stops a dental practice mid-procedure, and leaves a senior living building still owing its residents dinner. Stored water is the difference between an inconvenience and a closed day.

This is a cost question, not a fear question.
Work out your own number first. The decision follows from it.
Central Alabama Water (formerly Birmingham Water Works) runs a reliable system, and most years pass quietly. Main breaks and boil-water notices still happen, they arrive without notice, and they last hours to days.
The question is simply what a closed day costs you. Take your average day of revenue, subtract the costs a closed day spares you, and that is the number a storage system is competing against. For most restaurants one closed day lands in the same range as the whole installation. For a senior living building, staying open is the requirement.
Where the arithmetic points to waiting, we say so. That is a perfectly good outcome for a phone call.
Stored potable water, sized to the hours you need to cover
A booster to put it back into the building at working pressure
Disinfection on the way out of the tank
Backflow protection settled with the water utility, to the arrangement they require, before we quote
A published size chart — hours of cover times your actual draw is what sizes the tank