Waterbear, PoolSean, CarlD, et al, thanks for your wisdom on this. Actually, my original question was slightly different, but you answers were all helpful.

The original question dealt with any danger associated with leaving a puck tri-chlor feeder in line with an about to be installed SWG system with the puck feeder to be used as a backup in case the SWG had to be out of service for more than a few days. As I said, I'm away from the pool for many days at at time and, unfortunately, up to now I've had to rely on the puck feeder when I'm gone. So, I was looking for a way to quickly switch back to the puck feeder until I have the opportunity to get the SWG up and running again.

Based on all your responses, I think I'll remove the puck feeder and fit it with a pair of unions such that it's an easy drop-in replacement for the SWG cell. Total Cost = $15.

RE: replacement parts for the SWG; none of the local NW Florida (that's where my pool is located) pool stores nor distributors (as far as I can tell) carry the Auto Pilot line and I suspect there isn't a service center within 50 miles either. Conversely, I can get a pump, filter and other common parts within a hour. So, that's why I'm being a bit conservative in looking for a backup for the SWG.

Again, thanks all for your feedback, ideas and suggestions!