Managing high CH

[acroy]

it's expensive and a hassle to drain water, replace, dose it all back up with salt, borates cya.
Here are the current numbers, SWG in a gunite pool:
FC: 6
pH 7.6-7.8
TA 90
CH: 600 and climbing!
CYA: 80
Salt: 3000ppm
Borate: 40
Temp: 84f

Pool Calc does not raise any red flags - mild CSI positive. I watch for Calcium buildup around the water line and on the salt cell very closely, no issue. Normally i let the pH climb to about 7.8, then nuke it with pool acid back down to 7.6.

So - tips or tricks to deal with high ch? just keep an eye on pH, TA and make sure the Calculator is happy?

thanks & happy swimming!

 

[msgtdan]

Any rain you can divert to the pool will help lower CH.

 

[acroy]

I do divert what I can to the pool for free 0 ch water!
anything other tips msgtdan? the Alk sometimes gets quite low as I use straight muriatic to lower pH - pool calc does not like Alk 50

 

[Richard320]

Keep pH at the lower end of the comfort zone and throw the recommended levels out the window as far as TA and CH go. Watch the CSI.

600 CH looks pretty good to me.

 

[Dabby]

I currently have about the same test results as acroy. The CH has been steadily climbing ever since the pool was built 3 years ago. It is currently 650. I have a few questions I was hoping someone could help with.

At what point would a drain and refill be required? I am assuming that the CH is just going to continue to climb. In other words, how high is too high? I tested my fill water, and the CH is 100 and the ph is 8.0. I have to add several gallons of water a week because of high evaporation. Am I looking at having to drain and refill every few years?

Also, richard320, you said to throw out the recommended levels of TA. Are you saying to just keep the ph low and not worry about the TA, or should I keep TA on the low side also? And when you say keep the ph on the low end of the comfort zone, what range do you mean? It has not been easy keeping the ph as low as I should, mainly because the fill water's ph is so high.

 

[Richard320]

If you plug your numbers into the pool calculator, it will give you the CSI. But it also gives you "ideal" ranges for FC, TA, CH, etc. For some of us, a fresh fill is right to the upper limit for CH - that's why I said throw those numbers out the window.

So, you've entered numbers and it gives you CSI. Above about .6 and it will start forming. So you want to keep it closer to zero. You can't do much with CH. You can't do anything with temperature. You have a narrow range for pH. About all that's left to adjust to keep CSI neutral is TA.

From my experience, when CH gets around 900, that's when it becomes incredibly difficult to keep the pool from scaling. I run pH at the low end 7.2-7.5 and TA around 50-60. It goes up when I top off the water loss. That allows the high CH without it scaling. I try to drain and refill before than point, using it to water the lawn. And capture any rainwater I can, since it has no Calcium.

 

[Dabby]

I've read some posts that suggest to keep the CSI lightly negative to help with scaling. Would you recommend that?

 

[Richard320]

I've read some posts that suggest to keep the CSI lightly negative to help with scaling. Would you recommend that?

If you can, yes. And they were probably my posts you read :lol:

 

[Dabby]

Thanks so much for the information. I'll think about water replacement when I start to get up around 900.

 

[Patrick_B]

Personally, if I had 100 PPM CH and could use the water with any relative amount of freedom, I would never run the CH up to 900. I think it is just too risky if you don't have to do it. Maybe your water is expensive or limited, but CYA, Salt and Borates are really cheap in comparison to having Calcium scale. To my mind anyway.