Bama Rambler said:
You need to add enough bleach to get the FC to the reccommended level for the CYA you've added. The swg is not designed to bring the FC up from zero. It's designed to hold it there once you have it there.
I'd have to disagree with this statement. Salt systems ARE designed to bring the FC up from zero. It's just another form of introducing chlorine to a pool that tends to be a more convenient method than adding traditional chlorine products, for some pool owners. However, the consensus is to not allow the salt system to do this as it takes away from the cell life. Adding chlorine manually to get the chlorine level up is just a quicker way to get the chlorine introduced into the pool.
Same opinion with a salt systems BOOST cycle. Rather than using the salt system to boost the chlorine level (which is just another way of temporarily increasing the output to 100%), manually adding chlorine saves the hours of life on the cell.
All cells have a finite number of hours of operation. Once those hours count down, the cell needs to be replaced. Conditions that would accelerate cell depletion are running with low salt and/or stabilizer levels, regular use of the Boost cycle, improper water chemistry (pool saturation index which leads to scale formation in the cell WILL deplete the cell life even more rapidly), or undersizing the cell to the pool.
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Back to the original post, it's possible that the chlorine is getting consumed by some other chemical reaction, other than low cya. The use of any Specialty Algaecides, containing Sodium Bromide, will cause problems with salt chlorinators. Algae and high levels of Phosphates will also consume chlorine.
If there's a union that you can loosen after the cell, and take a water sample from there, test to see if it's higher at this point, than in the pool itself. That's a quick indicator as to if the cell is making chlorine.
I'm surprised it has not been suggested yet, but an overnight chlorine loss test can also help determine if you have some water chemistry issues, rather than the cell not working, or being able to generate enough chlorine.
