The differences in chemicals with an SWCG system are as follows:

1) They generally operate more efficiently with higher levels of CYA -- some manufacturers recommend 70-80 ppm, but this depends on the cell design so see what your manufacturer says.

2) They seem to be able to operate with lower chlorine levels, though this is hotly debated on this forum. Some users swear that one must still maintain levels according to Ben's Best Guess CYA chart, but most say that a level of 3 ppm works well even with 70-80 ppm CYA (which would normally require a minimum of 5 ppm from Ben's chart).

3) They require a minimum salt level in order to operate. The exact amount varies by manufacturer, but is typically in the range of 2500-3500 ppm of salt (NaCl) though technically it is chloride ion that is measured (and is what is relevant) even though it gets reported as ppm of sodium chloride salt.

If you do not have the minimum salt level in your pool, then the SWCG will simply not operate since there won't be enough condicutivity in the water without the salt to cause the electrolysis in the SWCG cell to happen (i.e. you won't generate chlorine). So don't bother turning on the SWCG until you add salt to your pool. In the meantime, use liquid chlorine or bleach and add CYA if it's not already there or else you'll lose the chlorine to sunlight too rapidly. Be sure that the TA and CH are up to the normal levels (around 100 and 300, respectively) since you have a gunite pool. Adjust pH, etc. -- all the stuff you would do with a non-SWCG pool.

Richard