Alkalinity at 200

[BoombaMon]

Hello TFP hive! I've been working hard getting our 'new to us' pool balanced. PH was 6.8 when we moved in and the plaster was coming off the walls. After adding, over the course of 4 weeks, about 32 lbs of PH up I've finally reached 7.5. Problem is now my alkalinity is at 200. I really don't want to use acid to bring it down as it took a lot of time and money to get the PH up.

Would you recommend I add the acid to lower the alkalinity, or just leave it alone?

 

[ajw22]

First of all, you need a better test kit. For our water chemistry advice you need the Taylor K-2006C or TFT Test Kits

If your TA is really 200 then your pH will rise above 8 within a few days. You will be frequently adding acid to keep your pH in the 7's.

High TA does not give you a stable pH.

High TA alone is not a problem. But high TA causes rapidly rising pH, scaling in a SWG, and possible plaster scaling.

PH - Further Reading

www.troublefreepool.com

TA - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

 

[Lake Placid]

As you’re feeding your Pool and Spa trichlor - high Alk isn’t of great concern (and it’s normally manageable anyway regardless). You’re going to face bigger concerns when you reach CYA overdose. After you line up a proper test kit, you should seriously consider alternative sanitation options whether it be liquid chlorine or a SWG.

 

[BoombaMon]

First of all, you need a better test kit. For our water chemistry advice you need the Taylor K-2006C or TFT Test Kits

If your TA is really 200 then your pH will rise above 8 within a few days. You will be frequently adding acid to keep your pH in the 7's.

High TA does not give you a stable pH.

High TA alone is not a problem. But high TA causes rapidly rising pH, scaling in a SWG, and possible plaster scaling.

PH - Further Reading

www.troublefreepool.com

TA - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

Thanks for the resources, Allen I've done a lot of reading on here and a better test kit is on order. For the first 3-4 weeks of owning the pool I compared my test results to the pool store's results and they seem to be pretty close to each other. Once this kit runs out I will start using the TFP recommended one.

As you’re feeding your Pool and Spa trichlor - high Alk isn’t of great concern (and it’s normally manageable anyway regardless). You’re going to face bigger concerns when you reach CYA overdose. After you line up a proper test kit, you should seriously consider alternative sanitation options whether it be liquid chlorine or a SWG.

Will be making a decision on new sanitation program soon, but for now I want to get the water balanced before making more changes. CYA is currently 50. Considering the desert climate, the extended periods of time we are away from the house, and the pool being treated the same way for 25 years, I am trying to find a good balance between liquid chlor and trichlor.

So...would you go through the hassle of ph up and down cycles to get the alk in line, or be okay with the high alk considering trichlor is being used most of the time?

Thanks for your help everyone.

 

[JamesW]

PH was 6.8 when we moved in and the plaster was coming off the walls. After adding, over the course of 4 weeks, about 32 lbs of PH up I've finally reached 7.5. Problem is now my alkalinity is at 200. I really don't want to use acid to bring it down as it took a lot of time and money to get the PH up.

CYA is currently 50.

The numbers really do not add up.

200 - 121 = 79 ppm TA.

At 79 TA and 50 CYA, the pH should have been good.

Even if the pH was low, it should have recovered way before 32 lbs of pH up.

Are you sure about the CYA at 50?

Was the CYA originally a lot higher?

 

[JamesW]

Try to keep the CSI below 0.3 to avoid scaling.

 

[BoombaMon]

The numbers really do not add up.

200 - 121 = 79 ppm TA.

At 79 TA and 50 CYA, the pH should have been good.

Even if the pH was low, it should have recovered way before 32 lbs of pH up.

Are you sure about the CYA at 50?

Was the CYA originally a lot higher?

View attachment 601460

I thought the same thing. My HTH kit measured CYA at 90, a few times in a row, but the pool store measured 50, a few times in a row, so I've been assuming 50 for now. Believe me when I say it was a big surprise that adding ph up 8 lbs at a time would raise by roughly 0.1 each time. This seemed crazy to me, but I kept going and it appeared to reach a tipping point where the ph finally went up enough. The house has not been occupied for 5-6 years (we just moved in two months ago) and the same vendor had managed the pool since construction. I was happy to see it was so "stable", but based on the amount of plaster getting picked up by the vacuum and pump filters, I figured getting the ph in balance first was priority. According to your screenshot above, the TA did exactly what it should. Ph just took forever.

Do you think TA at 200 while using the Trichlor tabs is okay if I'm not seeing rapid ph rising? Or would you swing back and forth until TA is in the suggested range?

 

[JamesW]

Try to keep the CSI below 0.3 to avoid scaling.

As long as the CSI is not higher than 0.3, you should be fine.

 

[JamesW]

My HTH kit measured CYA at 90, a few times in a row,

I suspect that 90 is more accurate than 50.

Low pH and high TA are usually consistent with high CYA.

The Cyanuric Acid acts as a type of Total Acidity, which is a buffer that reduces pH rise from added base.

The percentage of CYA/Cyanurate was maybe 50/50 and it went to 20/80.

So, 30% of the Cyanuric acid had to convert into cyanurate, which uses up a lot of pH increaser.

 

[JamesW]

Cyanuric acid contributes to the Total Acidity.

Cyanurate contributes to the Total Alkalinity.

At a pH of 7.5, the cyanurate contributes about 1/3rd value to the TA.

So, a 90 CYA contributes about 30 ppm to the TA.

Borates and Adjusted Alkalinity.​

Adjusted TA = TA – (CYA X CYA C.F) – (Borate x Borate CF)

Borate C.F (correction factor) based on pH.

pH.......CF

7.2.....0.051

7.4.......0.0786

7.6......0.1248

7.8......0.1989

Cyanuric Acid correction factor based on pH.

pH........CF

7.0.......0.22

7.1.......0.24

7.2.......0.26

7.3.......0.28

7.4.......0.30

7.5.......0.32

7.6.......0.33

7.7.......0.34

7.8.......0.35

7.9.......0.36

For example, if the pH = 7.6, TA = 90, Borate = 50 and CYA = 70, the adjusted alkalinity is 90 - (70 x 0.33) – (50 x 0.1248) = 60.66.

 

[BoombaMon]

Try to keep the CSI below 0.3 to avoid scaling.

As long as the CSI is not higher than 0.3, you should be fine.

Thank you for explaining the CYA/TA relationship. I've been dumbfounded as to why it took so much to get the ph up, but now it makes sense!

Just finished testing again and CSI is 0.19. So I'm just going to leave it alone for now and see if the TA lowers naturally. Thanks again for your help.