Reducing TA in <1yr plaster pool

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C

cgarai

0
May 5, 2014
9
California
Hi

Is my approach to lowering TA working as one should expect? Should I be doing this while my pool is only 10mo old?

I'm trying to get my TA down from 110 (it went as high as 150 during the first few months of the pool). I'm dropping the pH down to below 7.2 and aerating with a small bubble aeration disk pushing about .5CFM of air. It seems as though the TA is dropping very slowly and it is hard to keep the pH down. It is a little hard to tell how far below 7.2 pH I get because the scale on my test is 6.8 and 7.2. I'm worried about dropping it below 7, so I haven't seen the test fully down at the 6.8 color. I'm using full strength MA adding between 48 and 64 oz at a time.

Here is the acid additions and aeration time:
date pH TA MA added Aeration time
5/20 7.5 130 64oz 0
5/21 7.3 128 7
5/22 7.2 110 48 14
5/23 7.3 100 48 12
5/24 7.4 95 68 5+

The TA of 95 was measured 4 hours after acid was added.
The pH's listed are before acid addition


As I under stand it, I should be aerating with the cover off. Normally I keep the cover closed when not in use. It's not too windy where I am, but it is California so I'm trying to be very drought conscious.

Current Chemistry:
pH 7.0 - 7.2, before this I have been keeping it below 7.6
TA 90-100 was 130ppm at the start of aeration
FC 1.5-2ppm
CC 0 FAS/DPD
CYA 25-30ppm
CH 410 Pool was filled with well 220ppm well water, now maintained w softened water
Salt 3400ppm
Temp 73F

Thanks,

Chris
 
You are doing just fine. There is nothing to worry about with 10 month old plaster.

It takes time to get TA down, longer because you are keeping the pool mostly covered. But you ill get there eventually.
 
Thanks Jason,

Any harm in lowering the pH to 6.8 just so see what it looks like on the tester?

Here are some pictures of two aerators I created:

https://plus.google.com/photos/1023...ms/6152606820627027969?authkey=CNa8mvbl8OLbJQ

The venturi runs off the pool cleaner line. The aeration disk runs off a surplus air pump I had. To put air down at 8' you would need a pump capable of about .5-1 CFM at 3psi.

The venturi outputs about .5CFM while the air pump is putting out about 1 CFM. Both are very fine bubbles. The venturi is cheap to build, but is driven by a 1.5 HP pump. The airpump would cost around $50-$100 or more but only uses 100W

Thanks,
Chris
 
Low PH won't kill you, but it tends to be rather unpleasant, burning eyes and itchy skin. Most people are not happy swimming unless the PH is 7.2 or higher, though there is some variation from person to person.

The wait after adding acid is because the acid won't have mixed throughly and so the local PH might be far lower than what the PH will be after the acid is mixed in.
 
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