I would consider Stan's dose to be for system sanitation, but would not want to drink that much chlorine. I go by a dose that is stated in an oldbrochurefrom Everpure, Inc.about RVs and water.
Use 1/6th ounce (1 teaspoonful) of chlorine bleach to each 10 gallons of water. For a tank of 40 gallons, that would be .083 cups. This doses the water with 6.7 ppm chlorine, the recommended dosage for the quick-kill of harmful bacteria, viruses and slime-forming organisms. I dispensethe bleach with a squeeze bottle that measures 1/2 ozs into the hose prior to filling. You will also not have the chlorine smell hitting you if you drink it.
My local municipal water rates at 2.69 ppm with a allowance range of 0.61 - 4.58 ppm.
Again, this dose is for maintaining the health of your system and potable water.