CH and pH for a newbie

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Kglonghorn

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May 30, 2013
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I have been using this forum since I moved into my house with a pool already installed since last year. For the most part, I believe i had everything under control. I am in Houston with very high pH fill water and my SWG tends to raise my pH quite a bit. I was in the process of lowering the pH and TA to see if I could get it to stabilize, it tends to always run at 8.2 and TA 80. I had pH down to 7.2 and TA at 50, but kept rising so i gave up and just went back to having pH 8.2 and TA 70-80. Now I am seeing some white marking on the walls. I started checking my CSI, which I admit I didn't before, and now I see that with my pH at 7.2-7.4 and TA at 50, I was CSI<-.7, thus what I see on the walls must be the plaster etching Calcium out. OK, so now my question...When i put in pH 8.2 and TA 60-80, which is what it will run at if I don't do anything, this says CSI = 0.3 which is less than the max of 0.6. I was all about getting my pH low, because i read that I should, but is this telling me that I don't need to? So long as I stay below CSI=.6, I am ok?

ok as I read more...i realize what I posted above probably isn't good, I need a CSI near 0, so 0.3 isn't ok. I guess then I need to keep pH around 7.8 with a TA of 80. My pool won't stay like this so I guess I'll just have to add acid every couple of days. Am I understanding things right? I had hoped to get my TA low enough so my PH rise would "lock in" as I have read on here often, but in doing so I will get my CSI way too low, so maybe i just need to maintain manually every few days with acid.
 
The PH test reads any PH above 8.2 as 8.2. So when you are reading 8.2, the PH is usually higher than that.

You want the TA low and PH highish to slow down the PH increase, even if it won't completely stop the PH increase. You can raise CH a little to compensate if you want.

I very much doubt that what you are seeing is plaster etching, though I can't rule it out. Is your plaster colored? Etching would not leave white marks on colored plaster, but scaling would leave white marks.
 
Thanks JasonLion. I guess my concern is I got as low as pH of 7.2 and TA 50ppm and still my pH shot right back up to 8.2+. My next step before I saw the "marks" ,and I understand you think they may not be scaling, was to lower TA to 40 ppm and see if pH would "lock-in". The pool calculator would suggest that this is very much in the scaling zone for me. I really am struggling to keep pH stable and to do it without harming the pool. Any thoughts would be appreciated. Thanks
 
my CH is 290. I do have a waterfall from my spa ... and a small fountain in the shallow or wading end of the pool. When my pump is on high, i get some overflow from the spa/waterfall but not a ton, just enough to circulate the spa. I am currently testing only on low, to see how this affects ph.
 
I have the same thing happening...my pH is constantly rising. When you say it shot back up to 8.2 how many days did it take to go from 7.2 to 8.2? And was there any rain involved? I will also add that my own observations and searches I've done online indicate that chlorine is more effective as a sanitizer at lower pH levels so whenever mine hits 7.6 I try to lower it back to 7.2.
 
Gilrock, the whole "chlorine is more effective at lower PH" isn't really true any more once there is CYA in the water. There is still a very small effect, but it is to small to matter.

Kglonghorn, I suspected calcium scaling, but your CH level isn't really high enough for that.

Lower TA reduces the rate at which the PH goes up. Higher PH reduces the rate at which PH goes up.

If you add borates you can lower TA further than you can without borates.

Cutting down on how long the waterfall runs will also help significantly.
 
Ok so I have worked my TA back down to 70, my pH climbed from 7.2 - 8 in 5 days. I was planning to lower ph to 7.2ish so that I can lower TA to 60 and see again if it will lock in ph with my pump on low with little spa overflow. However when i punch in all my stats to the calculator, 7.2 and TA 70, I get a CSI = -.68 and when i put TA lower at 60 i get -.78. Is it even ok to do this? If not, i guess I have to add acid ever 3 days or so. My stats are included below. Thanks for your help.

FC = 6
pH = 8
TA = 70
CH = 260
CYA = 70
Salt = 3100
Borate = 0 (I have very young children so at this time I don't want to add borates)
Temp = 90F
 

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