3 Season history, and a question...

[steveinaz]

See my sig for pool details/testing tools.

Season 1 at opening, new pool (2007):
FC: *(Maintained at 8ppm)
PH: *(Maintained at 7.6)
CA: 225ppm
CYA: 50ppm
TA: 240ppm
Salinity: 2400ppm

Season 2 (2008):
FC: *(see above)
PH: *
CA: 425ppm
CYA: 65ppm
TA: 190ppm
Salinity: 2800ppm

Season 3 (2009, testing done 2/25/09):
FC: *
PH: *
CA: 525ppm
CYA: 62ppm (after adding 2lbs of HTH stabilizer)
TA: 90ppm
Salinity: 2600ppm

As you can see above, the pool is finally "settling down" and TA is finally dropping. I typically have to put about 3 cups of Muriatic acid every Saturday to maintain 7.6 ph; though recently, ph is holding much better. My SWCG calls for a salt range of 2250-2750ppm. I only test CA, CYA, TA, and Salinity levels once a year, at the beginning of the season (or if I adjust something).

My question: Should I be concerned with the Calcium Hardness level of 525ppm with a plaster pool? It doesn't appear to be having any effects on the pool as far as I can tell.

[chem geek]

You can calculate the saturation index using The Pool Calculator. Yours is currently around +0.1 so is fine. Last year you were at +0.4 and in 2007 you were at +0.1. So last year you could have had somewhat more scaling in your SWG cell (did you need to clean it more frequently?), but basically you are doing fine because the lowering of TA and the rising of CH essentially balance each other.

The pH is holding much better because the previously higher TA was causing the pH to rise more quickly. TA is a mostly a measure of the bicarbonate in your pool which is intentionally over-carbonated. When the TA is higher, the pool outgasses carbon dioxide faster and that causes the pH to rise more quickly. You could continue to have your TA get lower and your CH get higher over time though I wouldn't let the TA get below 60 unless you use 50 ppm Borates. Just use The Pool Calculator to roughly have the saturation index near zero though it doesn't have to be that close.

Richard

[steveinaz]

Thanks Richard. In the spring, both my filter elements and salt cell get a cleaning just as part of my routine. I never close the pool as it is so mild here in the winter, I just bring the SWCG down to 5% output and reduce filtering to 4 hrs a day.