I didn't really hit it with the mallet just gently tapped it just to loosen. I read several posts on this site about it and nobody seemed overly concerned about it. I'm really hoping to avoid cutting into the plumbing to get to the sand. From what I posted previously, does it appear that I have a channelling problem? I generally backwash weekly to twice a month. Would adding DE help or will it just channel through (if, indeed, I have a channel problem)?