Sustain & Automatic chlorinator question

First, I came across poolsolutions and this forum the other day and am overwhelmed by the wealth of information!

Several years ago we purchased a house that already had in in-ground vinyl liner pool with an automatic in-line chlorinator. The previous owner had bought into using a boutique brand of chemicals called Sustain, manufactured by PPG. The automatic chlorinator is a PPG/Sustain model and accommodate 3" tablets.

After doing some research the Sustain tabs are basically calcium hypochlorite tablets, not the commonly found tri-chlor tabs. Interestingly, PPG manufacturs essentially the same tablet (with possibly a different erosion rate) under their commercial Accu-Tab lablel. For a few years I was able to convince a local pool store to order me the commercial Accu-Tab tablets even though I wasn't a commercial account. For whatever reason the local stores I've dealt with can no longer order the Accu-Tab tablets.

With that background here are my questions:

1. I've seen warnings about not using any other tablet in the chlorinator but how serious is the risk? If I just let water circulate through the chlorinator for a week or so can I then use 3" tri-chlor tablets in the chlorinator?
2. Does anyone know of another source of 3" calcium hypochlorite tabs?
3. If I can't use tri-chlor tabs, and I can't locate calcium hypochlorite tabs, would it be worthwhile to change out the existing chlorinator with one that can use tri-chlor tabs?

Thanks.

You can use the same chlorinator after thoroughly cleaning the old one. Your method of flushing should be fine. I don't know of a 3" calcium hypo tab. Do keep an eye on your stabilizer level if you switch to trichlor, they add stabilizer and you may have to run higher chlorine levels as your stabilizer level increases. Trichlor is also going to drive your pH down as well. Most of us on the board love plain old bleach for chlorination, it only adds sodium to the pool.