What is Total Alkalinity (Adjusted) and other readings

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pcm2a

pcm2a

0
Aug 25, 2017
260
Mt Juliet, Tn
My pool guy used the pucks all summer and left me with a 125+ CYA. I got my own test kit around Christmas, Taylor K-2006C, and have been monitoring things myself. Through backwashing CYA is now down around 110 and with the rains I think this will be even lower before summer. I haven't added any chlorine in months, over the winter, until the other day. Free chlorine has gone down from 23 to 9, I put in bleach and raised it to 11.5 per the CYA chart. I took a sample just for fun to the local store and got hit with exactly the king of B.S. everyone says. I have a question about a couple of my readings and if I should put in any chemicals.

FC: 11.5, Store FC: 7.16 (I ran my test 5 times over two days, 11.5 all times)
CC: 0, Store CC: 0
pH: 7.5, Store pH: 8
TA: 70, Store: 62
Store Total Alkalinity (Adjusted): 26 (Will ask about this below)
CH: 180, Store: 147
CYA: 110 (guess since numbers only go to 100), Store: 108

Questions:

I know not to trust the store but why is their FC reading so much lower than mine?

My pH of 7.5 right in the acceptable limits. How long should I wait to take another pH reading?

My total alkalinity reading of 70 seems good but the store hit me with this Adjusted value of 26. They said it is because of my high CYA and want me to dump Alkalinity Plus into the water. Is this a real thing? I did some searches and came up empty.

My calcium hardness of 180 is under the recommended range of 200-500. Is it critical to add in some Calcium Plus for this? How long should I wait to check this reading again.

Thanks for the tips!
 
Believe your testing. I assume they did not use a FAS-DPD for their FC. All other tests will be incorrect above 5 or 10 ppm.

Believe your TA. They are doing some kind of calculation to sell over priced Baking Soda.

Your pH is not accurate with your FC above 10.

With a CH of 180ppm you need to add calcium. If your fill water is below 100 CH take your pool water to at least 300, soon. Only add half that is needed and test again in a few days to confirm.

You should do the extended test for CYA above 100 - see Pool School - CYA, Step 8

Be sure to read Pool School - Recommended Pool Chemicals

Take care.
 
Thanks for the info and I have some updates from the additional testing. I'm learning so much!

Last FC test was yesterday (11.5) today has been unusually warm, close to 80. FC is now at 10.
Extended CYA test (half tap water) is at 80. Using the same liquid I did the test 3 times.
Calcium hardness of my tap water is at 100. However, I'm not planning on adding tap water until it starts evaporating from the warm weather. I do expect a lot of rain water.

According to the link (pH of 7.5) I need to subtract 1/3rd of my CYA from the TA to get the adjusted TA, which gives me 70- 26.4 = 43.6 TA.

Now for what I need to do to get things in shape:

Do I trust the diluted CYA method of 80 over the non-diluted method that reads > 100? If so then my FC is perfect according to the CYA chart.

Adjusted TA of 43.6, the pool calculator says to add Baking Soda. I happen to already have a ton of it (my pool guy put it in when needed), will add that right away. Pool store wanted to charge me $30 for what was a few bucks worth of baking soda.

CH of 180 is low, but I know between April/May and October I will be adding a lot of tap water to the pool. Do I need to bring it up to 300 right now? Adding 10 pounds of calcium hardness would bring it up to 220. How quickly do I need to get it in there, meaning I can get 10 pounds from walmart for $20 today or 25 pounds off amazon for $30 but not until end of next week.

If my pH of 7.5 is not accurate with FC at 10, do I just leave the pH alone for now?
 
I would leave the pH as is.
CH. sooner the better. Your water is pretty aggressive and is pulling calcium out of your plaster. Luckily the water is cold so it is very slow.
CYA. You doubled the result you got, right? So with your diluted sample you read 40 in the vial. If so, leave it.
TA. I would not stress over the adjusted thing. I would not add any baking soda either. As long as you are no longer using Trichlor you will not have pressure on your pH and TA to drop.
 
Will get the CH added in today then. Looks like Leslies sells 25 pounds that should get my pretty close to 300. The pool store recommended to put in 6.5 pounds, wait a few hours and retest. This site (How do I Add Calcium Chloride to a Pool? | LIVESTRONG.COM) says 10 pounds per 10k gallons, which means I could add all 25 at once.

CYA, I got a reading of 40 three times and I doubled it to 80.

TA, I already added one 12 pound bag of baking soda. Will leave it at that and retest in a few days.
 
Adding the calcium is exothermic. It creates quite a bit of heat. Do in small amounts. At most do half the called for amount (in a few small batches) then give it a day or so and re-test.

- - - Updated - - -

Use PoolMath for your amounts for all chemical additions.
 
That is an excellent question. My pool guy and the pool repair guy that have both been around since the pool was put in told me 25,000 gallons. The pool is not square but I measured the length and a random width, pretended it was square and came up with closer to 20-22k gallons depending on what width I pick. Now I'm not sure which figure to use. Is it better to go higher or lower with a guess?
 

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Start at 25000.

You said you just added 12 lbs of baking soda. PoolMath says that will raise your TA by 34. See how close that is tomorrow.

Best way is the next time you add acid. Say your pH is 7.8. To drop to 7.5 you would need 18oz of 31.45% muriatic acid. Do that. Test about an hour later (pump running) and see if it matches. If it does not, use PoolMath to see how many gallons so that you get the real test result.
 
What is the best way to broadcast half of this 25 pound bucket in? The directions say not to predisolve it and not to use it on the same day as Leslie's soda. I assume that's their overpriced baking soda.

I put the 12 pound bag in 5 hours or so hours ago. I don't want it to all sink and turn into rock on the bottom.
 
Best this you can do is never let the pool store test your water, listen to their results, or listen to their directions on how to add or anything. Take their test results straight into the trash.

I'd run with 100 or 110 cya while it's cold and test your cya next month again, make sure you let the sample warm up and test it in outside and daylight. Then use that cya from then on.
 
Tested the water this morning and my TA went from 70 (not adjusted figure) to 110. Using the pool calculator a 12 pound bag of baking soda would do that for a 20,400 gallon pool. So I guess 20k would be more accurate than 25k.

Adjusted TA is now at 83.6. I'll add more to try to get it to 100, is that the sweet spot?

I dumped around 6 pounds of calcium hardness in last night and scrubbed the bottom with my leaf pole to stir up any white granules that made it to the bottom. Repeated with another 6 pounds this morning. Will repeat later on until I get all 25 pounds in. I took a CH reading this morning before adding the second 6 pounds and it came in at 190 which is not much change from yesterday's 180. Either yesterday's reading was off or it takes longer than 10 hours before I should have tested it. Pool calc says it should have jumped up to around 210.
 
I suggest waiting a couple days for your remaining Calcium. You can also use a 10 ml sample for testing CH. Each drop equates to 25ppm that way.

Your TA is now pretty high. Your pH will rise much more quickly with that high of TA. And, as you are maintaining your FC quite high due to high CYA, your pH testing is compromised. Keep all those factors in mind.
 
If TA should be between 60-120 or 80-120 then mine is either 110 or 83 (adjusted for high CYA). If there is no adjusted TA then I see how I could be on the high end. If there is no adjusted TA then should I now look into lowering it back down?

Also, if the pH reading is now compromised how would I maintain correct pH levels? Should I lower it to be on the safe side?
 
No need to actively lower your TA. It will lower each time you add acid due to rising pH.

At FC of 10 or greater the reagents for testing pH typically show higher than expected pH levels. As you now are testing your CYA at 80, you can allow your FC to drop below 10, and still follow the [FC/CYA][/FC/CYA]. When you see your FC below 10, be sure to test your pH and adjust to 7.5 or 7.6.

I would not stress on the adjusted TA thing. Only really matters (from the links shown earlier in this thread) if you have very high CYA and very low TA. You had and now have neither.

Take care.
 
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