Possible Problems of High TA

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
captjohn
Pool Newbie
Pool Newbie
Posts: 5
Joined: Thu 04 Jun, 2009 12:27
My Pool: Fiberglass, Indoor Glass Room, free form, jetted 15,000 gal, 1 1/2 HP Pentair pump, Triton 100 Sand filter, Chlorine system, Heat Siphon Heat Pump, auto chlorinator, waterfall and an 8' slide.
Location: Mississippi Coast

Possible Problems of High TA

Postby captjohn » Thu 04 Jun, 2009 13:29

I'm new to the forum but not pools. :wave: My question, other that causing the PH to creep up, what other adverse condition does a high TA cause? I have an indoor 15,000 gal fiberglass pool with the TA at 510 and the PH is 7.4. I have aeration built into the pool (slide, waterfall, jetted seating) so I'll try the aeration/acid method. My pool shop suggested the "slug" method.
I have well water with a lot of metal, and staining is also an issue. I use "metal out" as a maintenance item and "citric acid" to remove the stains and it's MAGIC. I use 68% Calcium Hypoclorite because of over stabilation issues. I don't get any rain water.
Any advice will be appreciated!
I'll definitely be spending time on this forum. :thumbup:


chem geek
Pool Industry Leader
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Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Possible Problems of High TA

Postby chem geek » Thu 04 Jun, 2009 13:46

Ascorbic acid would be better to use for removing metal stains than citric acid and yes, it's like magic. See this link for more info on that.

As you have noted, a high TA will result in a faster pH rise and this is accelerated by aeration such as the water features you mentioned. You should follow the procedure in this post to lower the TA. Do not use the slug method. It creates a VERY low pH locally and that can damage pool surfaces. The amount that TA gets lowered is solely based on the amount of acid that you add. The method of addition has nothing to do with that, but it does affect how quickly and efficiently and safely you can lower the TA. Acid lowers both TA and pH while outgassing of carbon dioxide raises the pH with no change in TA. So a combination of acid addition with aeration will lower the TA and doing this at a lower pH makes the process go faster. In 15,000 gallons, 4.8 cups of full-strength Muriatic Acid (31.45% Hydrochloric Acid) lowers the TA by 10 ppm. The only reason you don't add all the acid to lower the TA at once is that the pH would get too low and could damage pool surfaces and equipment.

The other problem with high TA is that it raises the calcite saturation index so can lead to scaling. This is especially true if the pH or Calcium Hardness (CH) are high. So continued use of Cal-Hypo that you are using will raise the CH and the water can become cloudy or scale can develop. It would be better for you to use chlorinating liquid or 6% unscented bleach if your saturation index is too high. You can use The Pool Calculator for calculating dosages and for the saturation index. You need a good test kit: either the Taylor K-2006 you can get at a good online price here or the TF100 kit from tftestkits.net here with the latter kit having 36% more volume of reagents so is less expensive per test.

Does your Metal Out product list any ingredients or does it have a manufacturer name on it? If it's EDTA, then this tends to break down faster and consume chlorine more while HEDP will not.

Also, are you using any Cyanuric Acid (CYA) in your pool? You said you are avoiding stabilized chlorine to avoid CYA buildup, but did you ever use any so you have at least some CYA in your pool? Even though it is indoors, a small amount of CYA (say, 20-30 ppm) will reduce chlorine's strength so that it isn't "too" strong. This will be less harsh on skin, hair, swimsuits and equipment. It should also lower the rate of some disinfection by-products, mostly nitrogen trichloride. You don't want too much CYA, however, because it would slow down oxidation too much if it were too high.

Richard
captjohn
Pool Newbie
Pool Newbie
Posts: 5
Joined: Thu 04 Jun, 2009 12:27
My Pool: Fiberglass, Indoor Glass Room, free form, jetted 15,000 gal, 1 1/2 HP Pentair pump, Triton 100 Sand filter, Chlorine system, Heat Siphon Heat Pump, auto chlorinator, waterfall and an 8' slide.
Location: Mississippi Coast

Possible Problems of High TA

Postby captjohn » Thu 04 Jun, 2009 22:07

I don't know if Ascorbic acid is ava. in my area but I will check. I have about 25# of citric left. I only use it 3-4 times a year, about 10# at a time. It does drop the PH dramatically though.
As for the Metal Out, it's distributed by Regal, http://www.regalchemicals.com/content/view/79/192/ . It only says it's a combination of chelating agents.
I read your posts and others before I asked this question. I'm a member of other forums and hated to ask a question that may have been asked 1000 times. The "calcite saturation" was what I didn't know about. I've learned a lot in the 1 day I've joined this forum. :thumbup:
As for the Cyanuric Acid, I use stabilized 3" tabs in my auto/chlorinator and it seems to keep a reasonable CYA level. I use the Cal-Hypo because I've had issues with CYA levels getting too high in the past. I used liquid chlorine years ago but it's not ava here. My calcium hardness does ride on the high side.
Thanks so much for the reply. I'm never too old to learn! :D
chem geek
Pool Industry Leader
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Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Possible Problems of High TA

Postby chem geek » Fri 05 Jun, 2009 02:02

Since you've got the citric acid and it's working for you, go ahead and use it. It is usually cheaper than ascorbic acid.

As for Regal Stain Out, the MSDS here just says "trade secret #1". So we don't know what it is. Again, if it's working for you, then great.
captjohn
Pool Newbie
Pool Newbie
Posts: 5
Joined: Thu 04 Jun, 2009 12:27
My Pool: Fiberglass, Indoor Glass Room, free form, jetted 15,000 gal, 1 1/2 HP Pentair pump, Triton 100 Sand filter, Chlorine system, Heat Siphon Heat Pump, auto chlorinator, waterfall and an 8' slide.
Location: Mississippi Coast

Possible Problems of High TA

Postby captjohn » Fri 05 Jun, 2009 08:40

I've read about using bleach since I can't find the liquid chlorine. I downloaded the "Bleach Cal".
I wonder if my test chems can go bad. I tested my water this morning and the CH was non existant. I find that hard to believe. I also keep strips on hand for quickies and it looks to be somewhere between 250 and 1000 (strips, need I say more). I'll replace my test kit today and retest.
My CYA was 100 (higher than I thought!) Auto/Chlor will be turned off. I read where you said the chlor level should be 7.5% of CYA and 20% for shock. Did I understand correctly?
TA 510
PH 7.4
FC 2
CC 0
I'll test my tap water for TA. Since I need to shock today, I may do a partial water change to lower CYA and maybe get a jump start on the TA. The water is BEAUTIFUL but I want to keep it that way.
Thanks so much for your help! :D
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Possible Problems of High TA

Postby chem geek » Fri 05 Jun, 2009 13:01

I sent you a PM responding to your PM. Get yourself a good test kit. Some of your numbers are definitely wrong from your PM (i.e. CH of 0 in pool water and CYA of 100 in well water).

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