As we know that water is a neutral substance so it contains both protons and electrons. a charged refill contains either protons or electrons it depends on the substance with which it has been charged. i'll explain with an experiment to you.
open the tap by which water will come out. bring the charged refill near it. you will see that the water bends a little towards the charged refill you have placed. this shows that the protons or electrons attract the other charge present in the water. this is because opposite charges attract and like charges repel each other.