What does buffer and added hardness do for a saltwater pool?

Answer 1

Buffer and added hardness do the same thing in a salt water pool as in a fresh water pool. The buffer (sodium bicarbonate aka bicarbonate of soda) stabilizes the pH of your pool so that addition of acid or base doesn't change the pH very much. The hardness, mostly Calcium, helps achieve water balance to make the pool neither deposit (precipitate) excess Calcium Carbonate to your pool surfaces nor corrode (remove) Calcium from your plaster pool surface. The combination of pH, Total Alkalinity (adjusted for Cyanuric Acid), Calcium Hardness, temperature and Total Dissolved Solids determines whether your water is balanced. Just keep these values near their recommended amounts for your pool and you should be fine. If you're a techie and want the full formulas, do a Google search for "Langelier Saturation Index".