Recently bought and filled a 7000gal vinyl pool with well water that was treated with a softening system using solar salts. Now I’m reading mixed things about using “soft” water. Some say not to use it, as it can be corrosive (but to vinyl?), others say that this is a myth. I have not added any chemicals or run the filter yet; however, I was planning to add the appropriate amount of stabilizer, raise the pH as necessary, and shock the pool, with the filter running over the next 24 hours. My questions are: 1) Is the soft water going to be a problem? Would the stabilizer add calcium back? 2) If it is a problem, what can I do, aside from draining and refilling?

Question:

Recently bought and filled a 7000gal vinyl pool with well water that was treated with a softening system using solar salts. Now I’m reading mixed things about using "soft" water. Some say not to use it, as it can be corrosive (but to vinyl?), others say that this is a myth. I have not added any chemicals or run the filter yet; however, I was planning to add the appropriate amount of stabilizer, raise the pH as necessary, and shock the pool, with the filter running over the next 24 hours. My questions are:

1) Is the soft water going to be a problem? Would the stabilizer add calcium back?
2) If it is a problem, what can I do, aside from draining and refilling?

Answer:

Low hardness levels can be a problem as it does promote corrosive water. A minimum calcium hardness level of 200 ppm is strongly recommended that way the water is not corroding metal fixtures, equipment and parts. The hardness can be adjusted by adding calcium chloride (hardness increaser) without the need for draining any of the water. The stabilizer will not add calcium back. Also, be aware that soft water may still contain some hardness (maybe as much as 50 ppm) so you may not need to add the full 200 ppm.