Easy setup using 1 Aqueous Accumulator / 1 Portable Tank / 2 Autonomous Activators, some EnderIO item conduit and an Item Filter.
Put Portable Tank on top of the Accumulator. First Autonomous activator pulls from portable tank with an empty bucket, sends filled bucket to second Activator. Second Activator r-clicks bucket on Petal Apothecary (needs to be aligned to base, not top).
Put in an item filter only to pull from second activator's inventory (back into first activator) only when the bucket is empty. This will pull empty bucket to be refilled with first activator and will be ready for next use.