Yeah, I had some very mild staining around the step area (fiberglass) last year. I guess that's why it got me thinking.

Besides getting calcium in there this year, I was just wondering if I could take it apart and clean up whatever might be starting - the exchangers aren't cheap and that's IF they're available at all.

Or do you think the calcium could abate the process?

Maybe I could get it apart and cycle some CLR (or equivelant) in there to clean it up? Just brainstorming here. I have the upper shells removed right now and it doesn't appear that it would be too difficult to get to the actual exchanger - just wondering if it will be a waste of time to try and do this.