Water Cloudy After Raising pH

franks59

Member
Aug 18, 2016
10
Columbia MD
Pool Stats:
30,000 gal gunnite pool
PCC 2000 system
INTELLIFLO 2 VARIABLE SPEED PUMP TRADE SERIES
STARITE SYS 3 MOD CART FILTER 450SF
SANIKING 940 PERFORMMAX CHLORINATOR

Sequence of events:

1) Pool company opened my pool and checked the chemistry. Said everything looked good except calcium hardness which was 150 and should be 200-300.
2) I double-checked the chemistry with my Taylor kit. I got:
Chlorine: 5
pH: 7.2
Total Alkalinity (TA): 65
Calcium Hardness (CH): 175
3) Since there was a difference in CH, I wanted to double check with another pool store in case my chemicals were too old, so I submitted a sample for testing. The results were:
TC & FC: 5.2
pH: 7.2
TA: 59
CH: 174
CYA: 87

Here's where it gets a little weird on several points - I should point out they are using BioGuard water analysis.
a) Even though the CH was low, they did not recommend adding calcium on advice from the manager who said with a white plaster pool, anything above 100 was acceptable.
b) The TA was low, but they say the recommended level is 125-150 instead of the 80-120 that I always see as ideal. They recommended adding 37 lbs of BalancePak 100 - baking soda.
c) They say the ideal pH is 7.4-7.6 which means my pH of 7.2 was slightly low. BUT.... the recommendation said my pH was TOO HIGH or would be too high after adding the baking soda.

4) All this being a little strange to me, I decided to do the following:
a) I added 10 lbs of Calcium Chloride. The CH went from 174 to 190.
b) The next day I added 1 13lb Costco bag of baking soda. The TA went from 60 to 90.
c) Today, I calculated that to raise the pH from 7.2 to 7.4 I would need about 4 lbs of soda ash. I decided to be conservative and add only 2 lbs. As soon as I started adding it, the pool clouded up and has stayed that way for several hours. The pH went from 7.2 to 7.3. Everything else stayed pretty much the same.

My current chemistry is:
Chlorine: 5.2
pH: 7.3
TA: 90
CH: 190
CYA: 87

I've seen suggestions that the cloudiness is caused by high alkalinity and/or high pH, and to solve the problem by lowering the TA with aeration, but everything seems to be within the proper range.
I've used all these chemicals before without a problem with the exception of calcium chloride.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,364
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
It is really unnecessary to use soda ash to raise pH. It is highly alkaline and raises both pH and TA very quickly. And because it's a powder, it doesn't mix very quickly so you get local "pockets" of high pH and TA pool water. This then causes the calcium saturation balance to go wildly positive which leads to scaling of calcium carbonate. That is the cloudiness you are seeing and it will take your cartridge filter quite some time to clear it up. At this point, there's not much you can do but filter the pool water.

You could have simply added the baking soda to raise the TA and the pH would have naturally come up on its own. Or you could have added borax to raise the pH without raising TA or causing any scaling.

Raising calcium hardness is also often totally unnecessary and can be problematic if you try to raise CH and pH too quickly or too close together. Many times, just allowing it to come up naturally will be more than adequate.
 
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