How to keep fluid inventory when breaking block with silk touch

Hi im trying to make a fluid tank that keeps its fluid inventory when its broken with silk touch tool. It has no gui and no inventory slots, just 3 different blocks that indicate the level of the tank. I tried setting global itemstack variable to convert block to item in the when block broken trigger for each tank and fluid type, however when i place any fluid tank state it reverts to its original state of fluid level 0 which triggers the update tick to show empty tank. It seems like a simple concept... Any help or ideas would be greatly appreciated, thanks!