Crazy Test Results - Who to Believe?

[johnsimion]

I live in Las Vegas. My 21K gallon pool has a SWG and the feed line is connected to my water softener to keep the calcium under control (it was partially drained and refilled in April using a mix of hard and soft water to get CH levels of 350-375). Unfortunately I got lax and I got a light dusting of algae two weeks ago for the first time ever. I freaked out and put the SWG on maximum, put chlorine tabs in the floater and put two bags of shock. The algae is conclusively gone and the pool is absolutely crystal clear ... but the chlorine level is ridiculously high. And that's really where my question begins.

According to the Taylor test kit using fresh R-0870 powder, my chlorine level at one point was over 50 (100 drops), so I turned off the SWG altogether for the last two days, figuring the Vegas heat would rapidly take it down. It didn't. By my measurement, today it was still only down to 32. Since I have guests coming in two days who will want to use the pool, I went to Leslies to get something to bring the chlorine down fast. I let them check things and that's where I got some really crazy results:
Chlorine: Me, 32.5 (64 drops to get clear). Them: 15
pH: Me, 7.2. Them: 7.6 (my pool constantly want a high pH, which results in high TA as well, so I added 2 gallons of acid two days ago)
TA: Me, 180 (2 days ago based on turning yellow due to high chlorine levels. I didn't test today). Them: 2 (they say TA "has been adjusted due to the effect of CYA").
CH: 350 (I didn't test today but this has been very constant in every test since April right up to my last test 5 days ago). Them, 184.
CYA: Me, 75. I didn't test this today but that test has given the same result since the partial drain and refill in April. Them, 106.

I should have retested after getting back from Leslies but I was in a hurry to put the "Chlorine Neutralizer" in the pool. Regardless, their results are waaaaay different from mine, to the point I don't have any idea what to believe. Their chlorine is still high, but only half of my own test. I would think my pH would be the correct one after adding two gallons of acid. The TA and CH make NO sense at all. I have NEVER had CH less than 350 at ANY time ever while using the Taylor test. And CYA ... that one is a hard one for me to do, but I've been using the Taylor test by sitting it on the bright light of my SpeedStir and looking down at it. It has come in at 75 doing it that way and I always understood that 75 was a good level for this pool, but at 106, Leslie's is showing me more than 25% too high. So who do I trust? Apparently CYA makes a big difference on how much chlorine I'm supposed to have.

There are more wild results. The Taylor salt test told me that the salt level was steady after the partial drain/refill in April, staying from 3400-3600 after adjustment until July, then inexplicably rising to 4000. In the three weeks since then, that figure has been steady. Meanwhile, the SWG reports no errors and since July it has been consistently showing a salt level of 3100-3300. I bought salt test strips today and they come out at 3500.

I will run a full battery of tests tomorrow morning after the chlorine neutralizer has a chance to work, but right now the extreme differences in these tests bothers me ... a lot. I've got people coming who want to use the pool and I can't even say how much chlorine I have, what I'm SUPPOSED to have, or anything else about this pool. And it bugs me all the more because I never had these issues before in almost 9 years.

Suggestions?

 

[DrewLG]

Believe your Taylor kit. If the reagents are much over a year old, maybe believe it less... But definitely believe it more then the Leslie's test in any case.

Your FC is exactly at the SLAM level (the upper threshold of the safe range) for your CYA concentration. In two days it'll be well into the safe range even without any chlorine neutralizer, so no problems for your guests.

Why'd you choose to do a panic shock addition instead of following the SLAM process to eradicate the algae? Clear water or no, you should perform an Overnight Chlorine Loss Test to confirm that the algae is actually gone.

 

[sande005]

To begin - your CYA testing may be wrong. See this article for details: CYA Testing - Further Reading
Using the speed stir light is throwing off your readings. While it should be bright sun out, it should be indirect coming in from the sides of the tube. CYA is not in between lines. If you can see the dot at 70, but it is gone before 80 - it is 80, not 75. See the article about the details of lighting, holding, reading the amount.

What shock, exactly, did you use? Along with the tabs, it may have thrown your CYA or other levels off, too.

Leslie's has a very poor track record of being even close - so they are the last ones to believe.
Test strips are also pretty poor, so not a lot of believability there, either. Better than Leslie's, but not by much.
How much, and what kind, of other chems did you add prior to the high salt test? All forms of Cl (except the SWG) increase salt in the pool. Granted, you would need a LOT to move it that far, that fast. But...
Are you counting drops for the salt test just up to that drop that changes things salmon pink?

Good luck with the Cl neutralizer - I used it back in my old bad days, and even when going gentle with 1/3 the recommended, it wiped out all the FC. And I had to add a lot to neutralize the neutralizer, and get back to a good level.

Sunlight, not heat, burns off the Cl. At 32, you would have dropped to below SLAM level (if your CYA is really right) the next day. And then be safe to swim.

 

[Bperry]

I live in Las Vegas. My 21K gallon pool has a SWG and the feed line is connected to my water softener to keep the calcium under control (it was partially drained and refilled in April using a mix of hard and soft water to get CH levels of 350-375). Unfortunately I got lax and I got a light dusting of algae two weeks ago for the first time ever. I freaked out and put the SWG on maximum, put chlorine tabs in the floater and put two bags of shock. The algae is conclusively gone and the pool is absolutely crystal clear ... but the chlorine level is ridiculously high. And that's really where my question begins.

According to the Taylor test kit using fresh R-0870 powder, my chlorine level at one point was over 50 (100 drops), so I turned off the SWG altogether for the last two days, figuring the Vegas heat would rapidly take it down. It didn't. By my measurement, today it was still only down to 32. Since I have guests coming in two days who will want to use the pool, I went to Leslies to get something to bring the chlorine down fast. I let them check things and that's where I got some really crazy results:
Chlorine: Me, 32.5 (64 drops to get clear). Them: 15
pH: Me, 7.2. Them: 7.6 (my pool constantly want a high pH, which results in high TA as well, so I added 2 gallons of acid two days ago)
TA: Me, 180 (2 days ago based on turning yellow due to high chlorine levels. I didn't test today). Them: 2 (they say TA "has been adjusted due to the effect of CYA").
CH: 350 (I didn't test today but this has been very constant in every test since April right up to my last test 5 days ago). Them, 184.
CYA: Me, 75. I didn't test this today but that test has given the same result since the partial drain and refill in April. Them, 106.

I should have retested after getting back from Leslies but I was in a hurry to put the "Chlorine Neutralizer" in the pool. Regardless, their results are waaaaay different from mine, to the point I don't have any idea what to believe. Their chlorine is still high, but only half of my own test. I would think my pH would be the correct one after adding two gallons of acid. The TA and CH make NO sense at all. I have NEVER had CH less than 350 at ANY time ever while using the Taylor test. And CYA ... that one is a hard one for me to do, but I've been using the Taylor test by sitting it on the bright light of my SpeedStir and looking down at it. It has come in at 75 doing it that way and I always understood that 75 was a good level for this pool, but at 106, Leslie's is showing me more than 25% too high. So who do I trust? Apparently CYA makes a big difference on how much chlorine I'm supposed to have.

There are more wild results. The Taylor salt test told me that the salt level was steady after the partial drain/refill in April, staying from 3400-3600 after adjustment until July, then inexplicably rising to 4000. In the three weeks since then, that figure has been steady. Meanwhile, the SWG reports no errors and since July it has been consistently showing a salt level of 3100-3300. I bought salt test strips today and they come out at 3500.

I will run a full battery of tests tomorrow morning after the chlorine neutralizer has a chance to work, but right now the extreme differences in these tests bothers me ... a lot. I've got people coming who want to use the pool and I can't even say how much chlorine I have, what I'm SUPPOSED to have, or anything else about this pool. And it bugs me all the more because I never had these issues before in almost 9 years.

Suggestions?

I thought I read somewhere the Leslies test tops out at 15ppm even if it was accurate? (it isnt)

 

[johnsimion]

"Believe your Taylor kit. If the reagents are much over a year old, maybe believe it less... But definitely believe it more then the Leslie's test in any case."
All my reagents were new earlier this year (2024) except for the salt test. You may be right about Leslie's but they do have a really high-tech machine (I haven't used them for testing for the entire time we've lived here until yesterday). I'll do my own full test of my water tomorrow and then take a sample to Leslie's and let them test the same sample just to see how it turns out.

"Your FC is exactly at the SLAM level (the upper threshold of the safe range) for your CYA concentration. In two days it'll be well into the safe range"
"Sunlight, not heat, burns off the Cl. At 32, you would have dropped to below SLAM level (if your CYA is really right) the next day."
I ALSO thought that would happen, especially in our 104 degree heat. The pool may not be entirely in full sun all day long but it is from 7 a.m. until at least 3 p.m. daily (and it's enough to heat the pool water to 90 degrees). However, my SWG was off already for 48 hours by noon today when I measured the chlorine at 32 by the Taylor test (i.e., 64 drops!).

"Why'd you choose to do a panic shock addition instead of following the SLAM process to eradicate the algae?"
Answer: I was dumb. First time ever getting any hint of algae = "panic" = dumb.
On 7/20, I first noticed the algae while I was in the pool. I measured the chlorine then at 1.5 which was way low. I immediately filled the floater with chlorine tabs, turned the SWG to max, brushed the sides and ran the pump 24 hours. I also added 1 gallon of acid because the pH had gotten somewhere over 8.2 and I read that the chlorine didn't work when it was that high. On 7/25 I measured the chlorine at 8. I couldn't see the algae anymore but at 8 I didn't trust that the chlorine was high enough to really kill the algae. This is why I added the two 1-lb bags of shock. I left the floater and the SWG at max for several days, which is why the chlorine got so high. First I took the floater out and turned the SWG down to 20% and reduced the time down to 8 hours a day. This didn't reduce it at all. I think it was at 75 then. Two days ago I turned the SWG off entirely so NO new chlorine was going in. After one day it measured at 65, I think (didn't write it down). After another day (today) I got a reading of 32. At this rate it would take two or three more days to get it down which is why I bought the "chlorine neutralizer".

"Clear water or no, you should perform an Overnight Chlorine Loss Test to confirm that the algae is actually gone."
As noted, chlorine hardly went down at all in two days since I turned off the SWG. Whether I'm dumb or not, the pool has been very clear now for more than a week already and I don't think ANYTHING could live in that pool.

"What shock, exactly, did you use? Along with the tabs, it may have thrown your CYA or other levels off, too."
My receipt says I bought two (2) bags of "Power Powder Plus Calcium Hypochlorite Pool Shock, 1 lb Bag." Leslie's ad says 73% calcium hypochlorite, non-stabilized, no CYA

"To begin - your CYA testing may be wrong. Using the speed stir light is throwing off your readings. While it should be bright sun out, it should be indirect coming in from the sides of the tube."
I asked somebody from TFP about using the SpeedStir light and was told it was good. I wanted to put the tube on the SpeedStir light because otherwise I find this test just about impossible to read. It's like, "Do I see the dot or not?" But you are right, the instructions you quoted say, "Outside in full sun or use the brightest indirect indoor light that you can if you have to test at night. I will retry tomorrow.

"Are you counting drops for the salt test just up to that drop that changes things salmon pink?"
I have been adding drops until it turns "completely clear." That is what the instructions for my Taylor test kit say -- I just rechecked them. Are you saying the instructions are wrong?

"How much, and what kind, of other chems did you add prior to the high salt test?"
Nothing but acid. Not since April after the 3/4 drain/refill. Added only stabilizer, salt and mix of hard/soft water then. My pool has never needed anything but acid.

 

[TinFoilHat]

Just stop already with Leslies and their products. Trust only the recommendations of TFP. Use liquid chlorine only and trust your Taylor kit and stop jumping back and forth. You're throwing your water balance way off by adding such large quantities of products without direction. Use the PoolMath app so you have guidance for your adds. One gallon of MA for a PH of supposedly over 8.2 probably took you below 7 which is not good for the pool. You want to keep it in the 7s. I add just 1 cup at a time to mine and a gallon lasts for a couple of weeks with a CH of 900+. I would bet that you would be in about the same position as me.

 

[sande005]

"Are you counting drops for the salt test just up to that drop that changes things salmon pink?"
I have been adding drops until it turns "completely clear." That is what the instructions for my Taylor test kit say -- I just rechecked them. Are you saying the instructions are wrong?

What salt test is that? Not the one in a TF-100 kit. In an online search I couldn't find one (any brand) that specs doing drops until clear.
Here's for the TF-100 salt test (emphasis mine):

Salt Test (Taylor K-1766 or TF Salt Test Kit)

PROCEDURE: CAREFULLY READ AND FOLLOW PRECAUTIONS ON REAGENT LABELS. KEEP REAGENTS AWAY FROM CHILDREN.

For 1 drop = 200 ppm Sodium Chloride

1. Rinse and fill the plain graduated cylinder to 10 mL mark with water to be tested.

2. Add 1 drop R-0630 Chromate Indicator. Swirl to mix. Sample should turn yellow.

3. Add R-0718 Silver Nitrate Reagent dropwise, swirling and counting after each drop, until color changes from yellow to a milky salmon (brick) red. Always hold bottle in vertical position. NOTE: Do not add enough R-0718 Silver Nitrate Reagent to give a brown color. First change from yellow to a milky salmon (brick) red is the endpoint.

4. Multiply drops of R-0718 Silver Nitrate Reagent by 200. Record as parts per million (ppm) salt as sodium chloride (salt water).

 

[johnsimion]

"One gallon of MA for a PH of supposedly over 8.2 probably took you below 7 which is not good for the pool."
Sorry, that may be true for most people but definitely is NOT true for me AND never has been in the last 9 years. I would add that I have never had a problem before this, either.

I know what the PoolMath computer says about how much acid to add, but I also know that doing what PoolMath says about acid has essentially no effect in my pool whatsoever - I tried for several months and it just does not work for my pool. One full gallon of acid in my pool barely makes my pH budge. In summer it takes a gallon a week to keep the pH below 7.8. And I am pretty sure I am right because I have added probably 3 gallons of acid in the last two weeks trying to bring the pH down below 8 and the TA down, and my Taylor kit yesterday said the pH was 7.2 while Leslies said it was 7.6. I am also almost certain the pH will be at 7.8 or more in a week. The pH rise may be related to the fact that the people who built my pool made the popups circulate water through the spa which then waterfalls into the pool every 10 minutes or so. I wish I could just turn the waterfall on and off as needed, that but so-called experts I've consulted basically say I'm stuck with things the way they are. My neighbor has a similar situation with his pool and waterfall overflow from the spa.

"What salt test is that? Not the one in a TF-100 kit."
My mistake, I misread your post. I was referring to the Chlorine test. I understand that the Taylor salt test has you add drops until it sharply turns brick red.

 

[TinFoilHat]

Ah, the waterfall will do that to PH. I aerate but that is only for 4 hours each night so my PH takes a few days to go up. Put up some pics of your pool equipment showing all of the plumbing and we can analyze that for you. Maybe there is a way to reduce your waterfall time.

 

[johnsimion]

I apologize for not responding sooner. Here are more results that seem more crazy than ever ...

As of yesterday (8/9), chlorine was "down" to only 11.5. I then swam in it to see just how bad it was (not bad, it didn't hurt my eyes when swimming extensively underwater). I just measured it now (8/10) at 7.5, which I also verified using the simple "basic" test. This is a full seven (7) days to get the chlorine down. During that week, my SWG has been completely "off", we had full Las Vegas sun every day AND I ended up adding nine (yes, 9) lbs of chlorine stabilizer. I have people who will be swimming in it tomorrow, so I will be turning on the SWG to 50% and see how that goes.

Thanks to all for the help. My experience disproves (to me, at least) that full sun does NOT make all the chlorine rapidly disappear. Of course, everybody's experience and everybody's pool is different. In the future, I will be much more careful never to let the chlorine dip as far down as it did. That was what let the algae start and my overreaction to it that led to all of this. I still don't know what caused the sudden rise in salt, but results have stayed pretty consistent at 4000-4200.

BTW, Leslie's tested my water again on 8/7. I had tested my chlorine at 27, they told me my chlorine was 18.2 but that they can't **print** anything higher than 15. So that is where the "15" comes from.

 

[sande005]

Wait - the last CYA you reported was either 75 or 100 reported at the beginning. We established that you might be skewing the numbers with your testing method. So what was the reason for adding 9 POUNDS of stabilizer???? That would add 57 ppm to the pool. If you were really at 75 or more to start, no wonder the sun wasn't burning off much!

 

[johnsimion]

Wait - the last CYA you reported was either 75 or 100 reported at the beginning. We established that you might be skewing the numbers with your testing method. So what was the reason for adding 9 POUNDS of stabilizer???? That would add 57 ppm to the pool. If you were really at 75 or more to start, no wonder the sun wasn't burning off much!

Egad! This is what I get when I write in a hurry while people are talking to me. "Chlorine Neutralizer." Sorry. No stabilizer was added. Three 3 lb. containers of chlorine NEUTRALIZER is what I added. And it worked, it just didn't work nearly as powerfully or as quickly as I expected.

 

[jmastron]

So ~7 days to go from ~21 to ~11, or about 3ppm/day? The effect of sun varies heavily with CYA level -- at, say, 30ppm CYA you might drop 4+ ppm/day of FC, while at 80ppm CYA that might be 1-2 ppm FC/day. I don't know what the chlorine neutralizer specs or actual effectiveness are, but that all sounds within expectations.

But your main conclusion matches TFP recommendations -- manage the pool so you are keeping the FC in range relative to the CYA at all times, and then there's never a need to thrash it with extremes. And if you do have an issue from not being high enough/algae, the methodical measured SLAM process is the best way to go. And, I'm sure others will suggest, primarily or exclusively using your own testing causes less stress...