Calcium

[Freegav]

Hi all.
Keen to understand your thoughts on ch levels. Mine currently at 225 measured on personal test kit.
Have a few calcium stains. Other numbers
Ph 7.6 always creeping up
FC 4
Cc 0
Cy 30
TA 120
Ch 225
Thanks

36000 l fibreglass black pool
swg. automatic acid doser.
cartridge filter. computer measures orp not fc
Melbourne Australia

 

[Texas Splash]

Based on the numbers you posted, your CH is currently within the acceptable level as noted on the TFP Calcium page for a SWG pool. As you noted, you'll always want to keep an eye on the rising pH to ensure it doesn't get out of hand above 7.8 since an elevated TA and pH, can accentuate the water's ability to produce scale - even in our fiberglass pools.

You could actually lower your TA much more (around 60-80 if needed) which should help keep the pH from rising too fast. Take a look at the TFP Pool School - Lower Total Alkalinity page for more details on that process. By managing all 3 (TA, pH, and CH) and keeping them in the acceptable ranges as noted on the link above, you'll do fine. Hope that helps.

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One final thought ... although you didn't mention it ..... you might consider looking at our TFP recommendation for CYA levels in a SWG pool (minimum of 70) which is especially important for an outdoor SWG pool in the summer to retain your FC.

 

[JoyfulNoise]

As TS alluded to, your TA is way too high. You can easily drop it down to 80ppm and probably have very stable pH (you might not even have to run the acid dosing system). Does your fill water have naturally high TA or are you adding something to keep it up?

You can use Pool Math to calculate CSI (calcite saturation index). As long as you keep your CSI between -0.3 and 0 (that means calcium is under-saturated in your pool water), then you should not experience any further calcium scaling. Keeping your water more aggressive than that, say between -0.6 and -0.3 could even reverse calcium stains if they are truly calcium stains and not something else.