When I setup mine theispast Sunday I filled with 5.5 gallons of 12.5 % chlorine. On season start up I manually dose the pool to bring FC up to my target and then set the flow rate, using a pinch valve on the Liquidator to a level that will replace the daily lose. This of course take a few days to dial it in, but I know after a couple of years that the pinch valve will need to be somewhere between 3 to 4 on the pinch valve setting scale. I usually refill the Liquidator with three or for gallons once the chlorine level reaches 2 inches from the bottom of the tank. So, under normal circumstances I have 2 to five gallons in the Liquidator. If I plan on being away longer than a week, then I will fill it up to the max level stated in the Liquidator operating manual.