Storage of Fresh Water - How Long

A lot depends on where you got the "fresh" water that filled your tank and how long it has been there. If it came from your local municipal water supply, chances are the water has been recently chlorinated and disinfected with ozone, UV, or whatever the local water treatment plant currently does. You can usually call them and ask if you want to know for sure. If the water came from a private well, that's not the case. It could be much better than municipal water, or much worse. Test kits are available. Google is your friend.

For me, if it looks bad (anything other than clear) smells bad, or tastes bad, dump it and flush the system with fresh chlorinated water. I drink/cook with RO (reverse osmosis) water.

Chum lee