We are planning to add a 250 gallon tank to our basement for emergency supply. We have water supply downstairs, but no drain (officially) due to city codes and the age of our house. The one drain we do have goes into our sump pit and is pump out into the yard away from the house. So, how important is it to change utility treated water on a yearly basis? Couldn’t I just recharge it with some bleach once a year?