Alkalinity - different between my test and pool store

[Kaltshuler]

I’m still fairly new to testing my pool myself so I sometimes have it tested at my local pool store. I’m generally very close. CYA is consistently a little lower when I measure vs the pool store. The bigger issue is alkalinity. I’m currently measuring alkalinity of 110 which is high for a salt water pool. However, the pool store is measuring alkalinity at 71 and suggests I raise it. The person at the pool store did say something about “adjusted” alkalinity, but when I questioned this he also showed me on a test strip that the results were closer to his reading than my reading of 110. I’ve tried wiping the tip of the bottle between drops when testing and I’m consistently higher.

Any thoughts?

 

[mknauss]

Welcome to the forum.
Pool stores play games with TA and suggest raising it way too much.
Read TA - Further Reading

Use your own testing. What test kit do you have? We will not provide guidance based on pool store testing.

I suggest you read through Pool School - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[YippeeSkippy]

Any pool store using strips to test customers water is not a pool store you want to test at. Actually, none of them are!
Your home kit is always more reliable, reproducible and easy to use right then and there.
Adjusted Alkalinity isn't what you want to know anyhow. How's your pH doing?? If its stable and not constantly rising on you I'd not worry overly about it.
Are you using Mineral products in your pool?? Ouch. High cost and risk of staining...beware.

Maddie

 

[Kaltshuler]

Thanks for the replies!

I have the TF-100 test kit I use at home. Generally my own measurements match what the pool store gets. I was just surprised about Alkalinity being so different.

Thanks for the link to more information about Alkalinity! Sounds like the pool store is reporting adjusted Alkalinity which would explain the difference. And to your point, sounds like they’re trying to get me to raise my Alkalinity too high.

PH levels are good.

And I’m not using the pool store chemicals. Using my own chemicals with the Pool Math app.

Thanks for the responses. Sounds like my measurements are probably just fine and I shouldn’t worry about double checking my readings.

 

[Texas Splash]

Using my own chemicals with the Pool Math app.

The APP and a good test kit. That's all we need to know.

 

[Drd]

I’m still fairly new to testing my pool myself so I sometimes have it tested at my local pool store. I’m generally very close. CYA is consistently a little lower when I measure vs the pool store. The bigger issue is alkalinity. I’m currently measuring alkalinity of 110 which is high for a salt water pool. However, the pool store is measuring alkalinity at 71 and suggests I raise it. The person at the pool store did say something about “adjusted” alkalinity, but when I questioned this he also showed me on a test strip that the results were closer to his reading than my reading of 110. I’ve tried wiping the tip of the bottle between drops when testing and I’m consistently higher.

Any thoughts?

The only time TA test might need adusting is due to higher levels of CYA above 30 ppm according to Taylor Chemicals. This is because above this point, CYA contributes more than a neglibale amounts to total alkalinity levels. Here is their statement;

False-high TA reading due to cyanuric acid
Cyanuric acid (CYA) titrates as total alkalinity when CYA is greater than 30 ppm. Adjust for this by subtracting 1/3 of your CYA reading from your total alkalinity reading to get the correct alkalinity value. For a more detailed explanation, refer to page 14 in your 2004B booklet.

Technical FAQs

 

[PoolStored]

The only time TA might not test accurately is if you used chlorine tablets that increase your CYA to a level it interferes with an accurate TA reading, but that wouldn't apply to you since you are using unstablized (no cya) liquid chlorine. The little base of cya you need in your pool won't cause this issue.

For clarity: The accuracy of the TA test is unaffected by high FC. Usually at high FC, you'll start with a green sample rather than a blue one after adding the R-0008. Then instead of the endpoint color change being the normal red it will change to yellow as the endpoint. If you know the FC is high, you can add a couple extra drops of R-0007 to eliminate this alternate color change (the R-0007 reagent neutralizes chlorine)

 

[Drd]

For Clarity, I am not making any correlations between FC and TA, only the amount of CYA tested levels in the pool water (PPM) and it's relationship to TA test results.

For example; my TA tested @ 110 ppm, but if you take into account I have 50 ppm CYA in my pool presently which is over the 30 ppm recommended, the TA adjustment goes like this; I would divide 50 ppm CYA by 3 which is 16.5 then deduct 16.5 from my TA of 110 resulting in an adjusted total TA of 93.5. Although the online "Pool Calculator" I use has a section that discusses this, it does not make this adjustment for you in the calculator itself. I was the one to bring this topic to their attention where they added a information peice on it so to speak, but did not incorporate into the programed TA and resulting balancing calculations, which are also used in determining CSI/LSI. But if you make the adjustment yourself and then enter the manual adjusted TA ppm into the calculator, you will get a more accurate assessment where you are at.

Note: I would check whatever source you use for checking your balancing or CSI/ LSI to see if their online pool water calculator does the TA adjustment calculations in the background for you or if you need to manually make the adjustment and then enter the adjusted TA ppm into the calculator or where ever you have your water checked. I took my water to a pool store and when I brought this up they refused to accept what I was talking about. I've also brought in my water and they tested it with number way different than my Taylor test did come to find out they needed to maintenance their water tester.

 

[PoolStored]

@Drd You modified your assertion after my response.

 

[Newdude]

Pool math makes any TA adjustments that are necessary for CSI. There is no other reason to alter what the Taylor test says.

 

[reggiehammond]

Can we talk about the low FC and the high CYA? This is an algae soup waiting to happen.
Ditch the minerals, stop going to the pool store, drain a good portion of water and go troublefree.

Right now, the water is not sanitary and needs a SLAM once the CYA is brought down for safety.
I’d get familiar with the FC/CYA chart ASAP.

 

[Newdude]

Also, the mineral springs beginnings and renewal they are suggesting are reallllllllllly overpriced bags of salt with a little CYA and borates sprinkled in. But it's 99%, $7 a 40 lb bag, salt.

I was on the mineral springs turnip truck myself. Falling off was a $800(?) a year blessing in disguise.

 

[Drd]

@Drd You modified your assertion after my response.

no I didn't I just replied to your critique of my original post. I was not referring to FC in my post.

 

[Texas Splash]

@Kaltshuler, as a relatively new member, let's start off once again by saying welcome to TFP! In your early TFP days, all the terms and recommendations may seem overwhelming. Let me assure you this will not last long. Armed with your TF-100 and the advice by many well-seasoned TFP members, you'll have that pool water in great shape before you know it.

So relax. Whenever you need chemistry advice, just post a full set of results or remind us to look at your Poolmath logs (linked by the way), so good job. There is no chemistry issue too difficult that can't be resolved by your TF-100 and TFP guidance.

Have a great Sunday, and let us know if you have any questions.

 

[mgtfp]

False-high TA reading due to cyanuric acid
Cyanuric acid (CYA) titrates as total alkalinity when CYA is greater than 30 ppm. Adjust for this by subtracting 1/3 of your CYA reading from your total alkalinity reading to get the correct alkalinity value. For a more detailed explanation, refer to page 14 in your 2004B booklet.
Technical FAQs

Just to make that clear, what Taylor describes here is not a "false-high TA". CYA contributes to Total Alkalinity, period. It is called Total Alkalinity, because it includes all sources of Alkalinity, including CYA-Alkalinity. That doesn't make it "false-high".

To use Total Alkalinity as a measure for for the number of Carbonate-ions in the water, that together with also present Calcium-ions can form Calcium Carbonate (Calcite) that can create scaling if the water is oversaturated with Calcium Carbonate, all other sources of Alkalinity (like CYA-Alkalinity or Borate-Alkalinity) have to get subtracted from Total Alkalinity to get Carbonate Alkalinity. Carbonate Alkalinity can be used to calculate the CSI (Calcite Saturation Index) that tells us how over- or undersaturated water is with Calcite.

Unfortunately, Pool Stores often subtract CYA-Alkalinity from Total Alkalinity and still call it Total Alkalinity. It is not Total anymore, once you start subtracting things from it. And double unfortunately, even a great company like Taylor adds to this confusion with this statement in their FAQs. What they mean is that the Total Alkalinity value that you got from the drop test needs to be corrected to Carbonate Alkalinity by subtracting CYA-Alkalinity to calculate the Saturation Index with their Watergram. Which is fine, I just wish they wouldn't still call it Total Alkalinity.

Poolmath does this conversion internally when calculating CSI. And so should the calculators that pool stores are using. There is absolutely no need to confuse customers with "adjusted" Total Alkalinity. Triple unfortunately, this works in their favour (and to the customer's financial disadvantage), as the "adjusted" TA will likely be below the traditional limits that they will recommend to correct by adding overpriced baking soda.

@Kaltshuler, no need to worry about all of that. Just use your TF-100 to test for TA (and other parameters), and use PoolMath. And have a good read through TFP's Pool School.