The Pool Calculator And Balanced Water

[sl3238]

If according to "The Pool Calculator's" Saturation index , my water is in "the balanced" range, does it matter what my PH and/or TA numbers are as long as I have enough sanitizer to be healthy enough to use? Are there absolute numbers above or below which PH/TA is unhealthy, regardless of the index?

[chem geek]

Unless the water chemistry parameters are way out of range, especially pH (pH of tears is around 7.5), the issue isn't your health but the possibility of metal corrosion.

The pH should normally be in the 7.2 to 7.8 range, usually 7.5 to 7.7 for hot tubs (the aeration of the water tends to have the pH be higher than 7.5). You don't want to go below 7.0 for extended periods of time as this risks metal corrosion. You don't want to be above 8.0 as the risk of scaling increases, though technically scaling won't occur unless the saturation index is positive and can occur at lower pH if the CH and TA are very high. TA should be at a level where the pH is stable. If you are keeping it low because you are using bleach (after using Dichlor initially), say 50 ppm, then you should probably have 50 ppm Borates in the water as well to provide additional pH buffering. The CYA should be in the 20-50 ppm range -- usually targeting 30 ppm. CH should normally be 120-150 ppm (or higher if needed to get closer to a zero saturation index) to prevent foaming.

Note that the recommended ranged in The Pool Calculator are for pools. For spas using the Dichlor-then-bleach method, the TA will be lower than the range shown.