2. To clean out a water tank, first thoroughly flush the tank using a bleach solution of 1 part 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).
A terrific Brown Glass Clorox 1 Gallon Bleach Bottle including the cap. This Clorox Bottle stands 12 inches tall and has a base diameter of 6 1/2 inches. The bottle has Clorox embossed on the front and back near the top. The bottom of the bottle is embossed with an "I in an O", the number "7", "Clorox and an 'R in a circle' all enclosed in a large triangle" and the numbers "7 and 55". The bottle was produced in the 1950's by Owens-Illinois Glass Company of Toledo, OH.