Rising CH - Causes?

[paulio]

Hello

It's been 5 months since we filled our new pool. Since then CH has been rising, which i gather is normal for a concrete pool. However, I tested my water the other day and these were the results:

CH 400
FC 6.5
TA 50
CYA 70
PH 7.6

The CH has risen by 100 since I last tested a month or so ago. We have had some hot weather recently and i have topped up the pool with water a couple of times since testing, our tap water has CH of 60. Is it possible that the fill water could have contributed to the rising CH that much.?

I should say also that when i brushed the walls the day before doing the testing, a bit of dust came off the walls so I wonder if the calcium could be leaching from the walls? Also i noticed a small amount of white crusty build up in placed underneath the coping. We have an automatic acid feeder so the PH doesn't usually rise that much but i don't know how much acid it's putting into the pool though....

 

[paulio]

HI All

After posting the above I saw another thread discussing this topic. After reading the topic I will plug my numbers and check the CSI and get back to y'all if i have any concerns

 

[paulio]

hi again
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After plugging my numbers into the poolmath I See that due to the salt requirement for my SWCG (currently level is 3800) my CSI is actually quite negative anyway. In fact it looks like I should let PH go up a bit and raise TA, would that be correct?

 

[chem geek]

Yes, that is correct, but I'd go easy on the TA, perhaps only get it to 70 ppm since you don't want your pH to rise that much over time. Your pH might settle in at around 7.7 or 7.8 which is also fine.

 

[paulio]

Thanks for that chem geek As for the rising CH do you think that a negtive CSI > 0.6 will cause CH to rise that quickly? or is it more likely evaporation + fill?

 

[Richard320]

Thanks for that chem geek As for the rising CH do you think that a negtive CSI > 0.6 will cause CH to rise that quickly? or is it more likely evaporation + fill?

CSI is just a number, an end result of some math; it's not an actual chemical value.

My take is that you are losing water via evaporation but the Calcium stays behind. That said, it could also be testing error. That CH test takes a lot of mixing. Lots and lots. Even with the speedstir doing it for me, sometimes when the color is just about to change, running it another cycle without adding any more R-0012 will get it to turn for me. The alternative would have been to add another drop or two and have it change. My CH readings dropped dramatically just by switching the test from manual swirling to using the speedstir.