How to Sanitize a Water Tank With Bleach

Here are some potential uses that may apply to your situation:

1. If you have a tank with clear water that you simply want to make sure is safe to drink or use for human contact (hand washing, laundry, etc.), then you can follow the protocol for emergency disinfection of drinking water. In that case, the correct ratio of bleach is ½ teaspoon Clorox® Regular Bleach₂ per 10 gallons of water (or for a smaller size container, 2 drops per quart). Stir the bleach into the water and let stand 30 minutes. Properly treated water should have a slight chlorine odor—if not, repeat the dosage and let stand an additional 15 minutes.

2. To clean out a water tank, first thoroughly flush the tank using a bleach solution of 1 part Clorox® Regular Bleach₂ per 150 parts water (a 500ppm bleach solution). I’m not sure of the size of your tank or how much bleach solution you will need, but here’s one example: if you want to make up 10 gallons of bleach solution, then you would start with 9 gallons + 15 cups of water, and then add 1 cup + 1 Tablespoon bleach. After flushing the tank with the 500ppm bleach solution, then rinse with a 10ppm bleach solution (1 teaspoon bleach per 10 gallons of water).

You may also want to get some chlorine test strips to confirm the bleach concentration of the solutions you mix up. These can usually be found at pool supply stores.