SWG and Puck Feeder?

[catnip]

I've read quite a bit on this forum about the dangers of mixing various forms of chlorine in the same feeder mechanism, but I haven't seen this question discussed before: Is it OK to have a puck feeder (Rainbow) in line with a SWG?

I ask this because I'm considering leaving the current puck feeder in line as a backup source of continuous chlorine in case my (about to be installed) SWG fails for some reason and has to be out of service for a while. I need some form of continuous feeder because I'm away from the pool for days at a time.

As an alternative to leaving the puck feeder in line, I've thought of fitting it with unions and just swapping out the SWG and screwing in the puck feeder in its place.

Thanks for any insight anyone has on this!