E.M.
Try to work around the fear of the drain. Figure out a way to neutralize the fear the drain causes. (Block it...cover it up...use magic or a spell to put it to sleep or render it powerless.) Your son may even help with the idea of what can help...if you can have a conversation with him.
The other idea is to just do sponge baths to take the stress of you and him until you find a way around the drain fear.