I currently use 1/2 a Campden tab every time for a 5-6 gallon batch. I was thinking if I can eliminate chlorine from the water by letting it sit, it may be better than adding a Campden to the water.
You'd only need 1/4 tablet per 5 gallons of water (1 tablet treats [EDIT]
20 liter or 5 gallons
20 gallons or 75 liters) but using almost double, as you do, won't do any harm.
I stir in a small, equivalent amount of Potassium Metabisulphite powder when I fill the bucket(s). It dissolves faster than a crushed tablet. I've never been able to taste it.
Can you be sure all chlorine would dissipate overnight, or even over 24 hours, from a (deep) bucket unless it gets stirred a few times?