Calcium hardness in swg

[grottoguy]

Why is the suggested CH in a plaster SWG higher than in a non-SWG plaster pool? Using the TFT test kit, my FC is 6.0; CC .5; TA 60, PH 7.8 (fluctuates a lot) ; CYA 60, but CH is only 250 (used to be 300 but has declined). I would have to dump a lot of Calcium hardness to raise my CH (pool is 40,000 gallons) to 300 and am deciding what to do. I have read that mixing it with water may prevent it clumping together on the bottom, but have also read that it will heat up fast that way. My pool water is 70 degrees and someone on this cite said in cold temperature it is more likely to clump. I guess my initial question is whether it is imperative that I raise my CH from 250 (note that my pool was just built in June so relatively new) and if so, should I just dump it in or mix it first.

Thanks

 

[duraleigh]

250 is not a dangerous level. CH will naturally climb over time so I would simply leave it alone.

What do you think has caused yours to decline? That's unusual.

 

[pooldv]

What is the CH of your fill water?

 

[JoyfulNoise]

One possible explanation for the difference in recommended CH levels is that often, in an SWG pool, pool owners find that the pH tends to rise very quickly so much so that acid additions are a daily event. If you notice the TA requirements are lower. That was changed recently to let folks drop their TA in order to get better pH stability. So, in order for the CSI to remain within safe ranges, the CH needs to be higher. Alternatively in could keep their pH at a higher value which would help as well.


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[grottoguy]

I will check my fill water tonight but suspect it's pretty low. I have no idea why it was declining unless the fill water perhaps was lower than the water that evaporated?

 

[JoyfulNoise]

I will check my fill water tonight but suspect it's pretty low. I have no idea why it was declining unless the fill water perhaps was lower than the water that evaporated?

Not possible. Even if fill water is 0ppm CH, the pool water CH would remain the same. CH is only lowered by water exchange.


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[grottoguy]

Not possible. Even if fill water is 0ppm CH, the pool water CH would remain the same. CH is only lowered by water exchange.


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I didn't follow that. How is Ch lowered? Only by taking out water and replacing it? My autofill overfilled my pool a coupleof weeks ago so i did take out water (but only a bout 3 inches or so).

 

[JoyfulNoise]

I didn't follow that. How is Ch lowered? Only by taking out water and replacing it? My autofill overfilled my pool a coupleof weeks ago so i did take out water (but only a bout 3 inches or so).

Ok. That's different. CH is only reduced by dilution. If you add low CH fill water just to replace evaporation, CH does not decrease. If high CH pool water is removed and replaced with lower CH fill water then CH decreases.


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