Beginner Water Testing Discrepancies

[SunnyFL]

I have been having bad experiences with my pool service companies so I am trying to do things myself. In the process of understanding water chemistry I was noticing some discrepancies in test results. I purchased a LaMotte ColorQ test kit hoping it would be easy and accurate.

In starting my learning I started by running samples to the pool store at the same time I ran the test to see if I was doing things correctly. I noticed discrepancies, so I took additional tests to other stores and the discrepancies continued. So, I got a little crazy and take testing to a wider scale... I decided to take samples to 3 different pool stores and run one myself (total of 4 tests) for two weeks in a row (8 total test).

Here are my results:

Week #1

	Test #1	Test #2	Test #3	Test #4
Tot Chlorine	4		8.22	6.69
Free Chlorine	4	4	8.22	6.69
pH	7.4	7.6	7.8	7.6
Alkalinity	120	110	94	80
Adjusted Alkalinity			75
Calcium Hardness	320	240	242	290
Stabilizer (CYA)	100	90	58	91
Tot Dissolved Solids	900	700
Phosphates		100	0
Iron			0	0.1
Copper			0.5	0.9
Week #2
Tot Chlorine	5	5	13.67	9.2
Free Chlorine	5	5	13.67	9.2
pH	7.6	7.6	7.8	7.5
Alkalinity	120	100	71	47
Adjusted Alkalinity			48
Calcium Hardness	375	200	288	316
Stabilizer (CYA)	100	99	69	115
Tot Dissolved Solids	1100	700
Phosphates		100	0
Iron		0	0	0.2
Copper		0	0.2	0.8

Test #4 is me, the LaMotte ColorQ. Test #3 is a pool store, but they are using the LaMotte Waterlink Spin Lab. Test #1 and Test #2 are general pool stores doing it the more ‘old fashioned’ way by matching colors.

As for the high chlorine in week #2, I shocked it the prior week and still had not come down. I expect test #1 and #2 only read 5 because I think that is the highest level on their chart.

I followed the standard cautions in my personal testing as noted in the ColorQ test kit (take samples after pump has been on for awhile, not take sample near jet, fill properly, keep out of light, test right away, etc.

Alkalinity, CH and metal’s looks particularly off. Chlorine off quite a bit the first week, reading 4's in both pool stores, but much higher in LaMotte tests.

I welcome any feedback about what to think of all this. My initial (though novice) opinion is the high variation is troubling to me but there very well may be some good reason for it or perhaps the variation is not something I should worry about - though the results suggest different treatments to the pool. Thank you in advance for reading all this!

 

[Texas Splash]

Hello and welcome to the forum! It's good that you did some homework and put together a variety of results to show what kind of variances we can experience. Even by the pool store alone we see that all the time. While we here at TFP do not rely on the LaMotte ColorQ for results, I would imagine it must be better than the pool store. Of those numbers however, two things jump out at me right away - elevated CYA and copper. Both detrimental to your pool. An elevated CYA makes it hard to sanitize properly and prevent algae, therefore the FC level must be increased. That can also effect the pH reading when the FC begins to hit 10 or more. Copper of 0.3 is an alarm for staining, or changing color in hair/nails. To see that much copper, you'd have to look back and think of how it got in the water - more than likely pool store products. Either algaecides or chlorinated products with copper in them (i.e. "Blue-something"). Also, your iron level appears to be elevated as well, and that's usual from your area.

As a new member, we value your participation and certainly want to help where we can. The first thing we would ask you to consider is replacing the LaMotte tester with a TF-100 or Taylor K-2006C. Either of those have proven themselves time & time again in this forum as they are accurate and consistent. So there, I said it. :blah: Ha. The only way to lower CYA (and copper) is to do a water exchange. Easy math ... if someone's CYA is 100, then changing 50% of the water will make the new CYA 50. Also, remove the tablets. They are packed full of stabilizer and raising your CYA by the day. Stick to "regular" bleach - aka chlorine. Same thing without any side effects.

Don't worry about TDS or Phosphates, just: FC, CC, CYA, PH, TA, CH. Those are what the TF-100 or Taylor K-2006C will test accurately for you. Please enjoy the forum, look around, and read our Pool School section to learn more about TFP. If there's anything else we can help with just let us know.

 

[Uncle Salty]

Hi and welcome to the forum. I to as a new pool owner last year before I found TFP was using a Lamotte ColorQ and although it’s easy to use it just isn’t accurate or repeatable enough to trust the results. Order yourself the TF-100 if you truly want a trouble free pool!

Salty

 

[SunnyFL]

Thanks for the info! I just ordered at TF-100. The high metal is probably as you suspected. I have some black algae spots which the prior (2) service companies were not solving and probably just dumping in treatment for increasing the metal. I will need to do the water replacement as suggested to reduce the CYA.

The TF-100 doesn't test for any metal what is the best way to test for that? The ColorQ seems to generate a result so maybe just continue to use that as it will provide at least a relative indication of whether my metal count comes down.

We have had a pool for 20 years and never had any algae problems until now. I have had a recent string of really crappy pool service people causing a wide variety of issues. The algae issue is a separate but related topic of course.

 

[Texas Splash]

The TF-100 doesn't test for any metal what is the best way to test for that?

Because metal testing kits are a bit more specialized, they can also be more expensive. So often times we just let the pool store do that one and ignore everything else they say. :blah: :blah: :grin: It's probably still not totally accurate, but gives us an idea.

We have had a pool for 20 years and never had any algae problems until now.

That's actually not unusual to hear. A big part of that comes down to how often the owners chlorinate, with what product, and where they live. For example, FL can get lots of rain, therefore overflow and water exchange can help some owners who were using tabs and not even know it. Some states simply don't receive the blazing sun we do down south, have access to plenty of water (perhaps lots of backwashing) so they don't need or build-up a high CYA or elevated FC. In your case, it was probably a combination of things. But now that you know, it won't happen again because the only time you will add stabilizer (CYA) is when YOU want it to go up - not as a by-product. Good job on the TF-100. You'll be glad you did. When it arrives, make sure to do a diluted CYA test as noted on the TFP Pool School - CYA page, stating at Step #8. Report back and let us know how it goes. Have a good day.

 

[Kiss4aFrog]

Welcome to TFP SunnyFL

Sounds like you're on the way to better managing your pool. Can you post a photo or two of the black spots ??

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