High Alkine, nothing lowers it, pH is fine! Help!

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
lsheridan
Pool Newbie
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Posts: 2
Joined: Tue 28 Jun, 2011 15:38
My Pool: 16 x 32 in ground pool, sand filter, vinyl surface, Hayward pump, filled with water softened water (no choice)
Location: Ohio

High Alkine, nothing lowers it, pH is fine! Help!

Postby lsheridan » Tue 28 Jun, 2011 15:46

Our pool alkalinity level is at least 240 (per the test strip) and it stays there no matter what I do. I've added about 8 lbs of reducer over time, to lower alkalinity, it doesn't touch it. However, pH still stays at 7.4-7.8. I can add a bag of shock every couple of days and I will still have little to no chlorine in it. The pool store says don't worry about it as long as the ph is fine. That worked last summer but this summer I just can't get my chlorine levels up. The water looks great most of the time, sparkling and clear. I still keep adding shock or chlorine hoping it doesn't turn green or cloudy but it's costing way too much with no results! We do have to fill our pool with water softened water since whoever owned the house before us apparently had the softener hooked to the main. No straight well water in this house or outside hoses for that matter. Any suggestions?

Additional note: Out of curiosity, I just tested my kitchen sink water with the pool test strips. Almost the same readings, pH was 6.8 instead of 7.8, alkaline 240, stabilizer 30-50, and no chlorine. Basically the same as the pool water after chemicals. Any suggestions on how get the alkaline down and raise the chlorine?


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

High Alkine, nothing lowers it, pH is fine! Help!

Postby chem geek » Tue 28 Jun, 2011 20:40

Follow the procedure in this post which is a combination of acid addition with aeration at low pH. You should really get a better test kit -- test strips are not very accurate. Get either a Taylor K-2006 or a TFTestkits TF-100 .

Try using chlorinating liquid or 6% unscented bleach. You need to add chlorine every day or two if your pool is exposed to sunlight. If your CYA is high, you'll need to dilute the water with partial drain/refill(s) to lower it. Higher CYA makes the chlorine less effective. Your FC level (at its lowest point) for a manually dosed pool needs to be at least 7.5% of the CYA level.
lsheridan
Pool Newbie
Pool Newbie
Posts: 2
Joined: Tue 28 Jun, 2011 15:38
My Pool: 16 x 32 in ground pool, sand filter, vinyl surface, Hayward pump, filled with water softened water (no choice)
Location: Ohio

High Alkine, nothing lowers it, pH is fine! Help!

Postby lsheridan » Tue 28 Jun, 2011 20:43

Thanks, I'll see about a new test kit and give it a shot. This may be a dumb question, but....is aeration just running the pump/jets?
Guest

High Alkine, nothing lowers it, pH is fine! Help!

Postby Guest » Sat 03 Sep, 2011 16:48

lsheridan wrote:Our pool alkalinity level is at least 240 (per the test strip) and it stays there no matter what I do. I've added about 8 lbs of reducer over time, to lower alkalinity, it doesn't touch it. However, pH still stays at 7.4-7.8. I can add a bag of shock every couple of days and I will still have little to no chlorine in it. The pool store says don't worry about it as long as the ph is fine. That worked last summer but this summer I just can't get my chlorine levels up. The water looks great most of the time, sparkling and clear. I still keep adding shock or chlorine hoping it doesn't turn green or cloudy but it's costing way too much with no results! We do have to fill our pool with water softened water since whoever owned the house before us apparently had the softener hooked to the main. No straight well water in this house or outside hoses for that matter. Any suggestions?

Additional note: Out of curiosity, I just tested my kitchen sink water with the pool test strips. Almost the same readings, pH was 6.8 instead of 7.8, alkaline 240, stabilizer 30-50, and no chlorine. Basically the same as the pool water after chemicals. Any suggestions on how get the alkaline down and raise the chlorine?

lsheridan wrote:Our pool alkalinity level is at least 240 (per the test strip) and it stays there no matter what I do. I've added about 8 lbs of reducer over time, to lower alkalinity, it doesn't touch it. However, pH still stays at 7.4-7.8. I can add a bag of shock every couple of days and I will still have little to no chlorine in it. The pool store says don't worry about it as long as the ph is fine. That worked last summer but this summer I just can't get my chlorine levels up. The water looks great most of the time, sparkling and clear. I still keep adding shock or chlorine hoping it doesn't turn green or cloudy but it's costing way too much with no results! We do have to fill our pool with water softened water since whoever owned the house before us apparently had the softener hooked to the main. No straight well water in this house or outside hoses for that matter. Any suggestions?

Additional note: Out of curiosity, I just tested my kitchen sink water with the pool test strips. Almost the same readings, pH was 6.8 instead of 7.8, alkaline 240, stabilizer 30-50, and no chlorine. Basically the same as the pool water after chemicals. Any suggestions on how get the alkaline down and raise the chlorine?
auzmob

High Alkine, nothing lowers it, pH is fine! Help!

Postby auzmob » Wed 14 Sep, 2011 03:45

what u can do is work out how much acid you need using a test kit to adjust the T/A ,top up the pool first then add acid in deep end diluted adding no more than 4lts every 6hours for 50.000lts pool untill the T/A is down to 100 .when u hit that mark wait a day then test for ph .it will bounce .etc 6.5 or less .then add soda ash half a kilo at one time for 50.000lts of pool water every 2-4 hours until u reach 7.4 -7.6 . then it will be easier to maintain ph from then on .dont leave pool with a low ph for long periods of time during adjustment
chem geek
Pool Industry Leader
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Joined: Thu 21 Jun, 2007 21:27
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High Alkine, nothing lowers it, pH is fine! Help!

Postby chem geek » Fri 16 Sep, 2011 02:00

auzmob wrote:what u can do is work out how much acid you need using a test kit to adjust the T/A ,top up the pool first then add acid in deep end diluted adding no more than 4lts every 6hours for 50.000lts pool untill the T/A is down to 100 .when u hit that mark wait a day then test for ph .it will bounce .etc 6.5 or less .then add soda ash half a kilo at one time for 50.000lts of pool water every 2-4 hours until u reach 7.4 -7.6 . then it will be easier to maintain ph from then on .dont leave pool with a low ph for long periods of time during adjustment

That is not good advice. You would never add acid and then add soda ash. If you want to lower the TA, then adding acid will do that, but you then want to aerate the water (or just wait) for the pH to rise with no change in TA (the proper procedure for lowering TA is described in this post). If you add soda ash, you will not only raise the pH and the TA, but the TA will be raised by MORE than it was originally. This is because soda ash is equivalent to a combination of lye and baking soda. Acid and lye exactly counteract each other, leaving only salt. For those who know chemistry, the following is what happens with what you were recommending:

Na2CO3 + H2O ---> NaHCO3 + NaOH
Sodium Carbonate (soda ash) + Water ---> Sodium Bicarbonate (baking soda) + Sodium Hydroxide (caustic soda; lye)

HCl + NaOH ---> NaCl + H2O
Hydrochloric Acid (muriatic acid) + Sodium Hydroxide (caustic soda; lye) ---> Sodium Chloride (salt) + Water

The net result is the same as adding baking soda and salt so if you were balancing the pH then the TA could actually rise instead of getting lowered, depending on aeration rates. Let's use a concrete example using your numbers.

pH 7.5 TA 200
Add 4 liters full-strength Muriatic Acid (31.45% Hydrochloric Acid) to 50,000 liters
pH 6.8* TA 160
Add 4 liters acid to 50,000 liters
pH 6.4* TA 120
Add 2 liters acid to 50,000 liters
pH 6.2* TA 100
*In practice, due to carbon dioxide outgassing, the pH won't get this low, but how quickly the pH rises from these values depends on the amount of aeration in the water. Let's assume that the pH is at 6.8 and you now need to add soda ash to raise it to 7.5.
pH 6.8 TA 100
Add 0.5 kg soda ash to 50,000 liters
pH 6.9 TA 109
Add 0.5 kg soda ash to 50,000 liters
pH 7.0 TA 119
Add 0.5 kg soda ash to 50,000 liters
pH 7.2 TA 128
Add 0.5 kg soda ash to 50,000 liters
pH 7.4 TA 138

So in this example due to the high TA starting point and assuming that there was carbon dioxide outgassing that kept the pH from getting below 6.8, we did end up lowering the TA, but also raised it higher than need be -- i.e. it went back up some due to the soda ash. So let's repeat the process at this point and see what happens.

pH 7.4 TA 138
Add 2 liters acid to 50,000 liters
pH 6.9* TA 118
Add 2 liters acid to 50,000 liters
pH 6.6* TA 98
Let's now add soda ash and assume minimal aeration of the water so the pH didn't rise from the above acid addition.
pH 6.6 TA 98
Add 0.5 kg soda ash to 50,000 liters
pH 6.64 TA 108
Add 0.5 kg soda ash to 50,000 liters
pH 6.7 TA 117
Add 0.5 kg soda ash to 50,000 liters
pH 6.8 TA 126
Add 0.5 kg soda ash to 50,000 liters
pH 6.9 TA 136
Add 0.5 kg soda ash to 50,000 liters
pH 7.0 TA 145
Add 0.5 kg soda ash to 50,000 liters
pH 7.1 TA 155
Add 0.5 kg soda ash to 50,000 liters
pH 7.2 TA 164
Add 0.5 kg soda ash to 50,000 liters
pH 7.4 TA 174
So in this second-pass case, the TA ended up higher at 174 than we started at 138!

Basically, your procedure was only half right. You definitely need to add acid to lower the TA -- that is the only way that TA gets lowered (other than dilution with water lower in TA). However, you should NOT add soda ash to raise the pH, but should aerate the water to make the pH rise faster and should keep the overall pH low until the TA target is reached. Also, one should be careful not to let the pH get too low though the lower the pH the faster carbon dioxide will be removed from the pool. If you followed this correct procedure, you would use less acid overall and no soda ash. You need more acid with your method because you have to use additional acid to compensate for the TA you are adding with the soda ash. Aeration increases carbon dioxide outgassing which raises the pH with no change in TA.

Also, when adding acid or chlorine to the pool, one should add it slowly over a return flow in the deep end with the pump running. Then lightly brush the side and bottom of the pool where it is added to ensure thorough mixing.

If one follows the proper procedure for lowering TA, then the following occurs:
pH 7.5 TA 200
Add 3.6 liters of acid in 50,000 gallons to get to a pH of 6.8
pH 6.8 TA 164
Aerate the water to get pH to rise to 7.2
pH 7.2 TA 164
Add 2.2 liters of acid in 50,000 gallons to get to a pH of 6.8
pH 6.8 TA 142
Aerate the water to get pH to rise to 7.2
pH 7.2 TA 142
Add 1.9 liters of acid
pH 6.8 TA 122
Aerate the water to get pH to rise to 7.2
pH 7.2 TA 122
Add 1.7 liters of acid
pH 6.8 TA 106
Aerate the water to get pH to rise to 7.2
pH 7.2 TA 106
Add 0.6 liters of acid to get pH to 7.0 (don't need to overshoot)
pH 7.0 TA 100
Aerate the water to get pH to rise to 7.4

Total acid with the correct method is 10 liters of acid. This is because 1 liter of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 50,000 gallons lowers the TA by 10 ppm. With your method, the initial acid addition to get to a TA of 100 used that same amount of acid, but then adding soda ash raises the TA where for every kilogram of soda ash you use you would need to add 1.9 liters of acid to lower the TA back down. It is this latter step that is a complete waste of money and effort that could be completely avoided by aeration of the water to accelerate carbon dioxide outgassing. If at the end of the procedure you have trouble raising the pH by aeration alone (because the TA is now lower making the rate of carbon dioxide outgassing slower), then use 20 Mule Team Borax (same as ProTeam® Supreme ) or caustic soda / lye / sodium hydroxide to raise the pH instead of soda ash. These pure bases will raise the TA only half as much as soda ash.

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