How long to keep potable water in holding tank

Chlorine dissipates over time. How good is your city water to start with (ever tested it)? It takes just one rogue bacterial cell to multiply. Warmer outdoor temps. can accelerate bacterial growth. How well is your holding tank and piping sanitized? If it were me, I'd use bottled water for drinking only. Filtration is an option if you use the right type of cartridges with max. 1 micron filtration (absolute rating, not nominal). Filtration can be point of use (POU) at the kitchen counter.