fill water TA 500!! Richard, Carl, Evan, Al help!!!

[chem geek]

First, why is there Free Chlorine in your fill water -- 2 ppm after the water softener and 6 ppm before? It sounded like you are getting the water from a well, but is it from some other local source or are you chlorinating it?

Second, the difference in TA between your two measurements is completely explained by the difference in pH. A pH of 7.6 with a TA of 500 is identical to a pH of 6.87 with a TA of 390 in terms of having the same amount of total carbonate in the water. So in essence, your water softener is ONLY substituting the calcium (and magnesium) in the water with sodium and/or potassium. It isn't changing your carbonate.

I don't quite understand why your water softener has raised the pH of the water. Your pre-to-post numbers are consistent with having 7.3 pounds of caustic soda / lye / sodium hydroxide added per 10,000 gallons.

As for which is better, the decision should really be based solely on the difference in calcium hardness and other benefits such as removal of metals. If there are indeed metals in the water, then using the post-water-softener would be best. If not and if you have a plaster pool, then using the pre-water-softener will get you the CH you need without having to add any calcium chloride (for a vinyl pool you won't need as much calcium).

Either way, you are going to have a heck of a fun time getting your TA lowered. The good news is that aeration will rather quickly outgas carbon dioxide so it won't take long to get the TA down, though it will take a LOT of acid, about 93 cups of Muriatic Acid per 10,000 gallons (over an extended period of time while aerating and keeping the pH low around 7.0 until your TA reaches 100 and then continuing to aerate without adding acid to let the pH get up to 7.5).

Richard