A pool that hates chlorine

[FrankieKat]

BTW, 1 gallon of 10% liquid chlorine, will only add 5.6 ppm of chlorine in 18000 gallons of water. If you have Algae, and I suspect that you do, that 5.6 ppm will be consumed quickly, with a CYA of 70, your minimum chlorine is 5ppm (anything less than 5 will give Algae a chance to grow) and your target is 8-10 ppm.

So, I've been pouring in a gallon a day just to keep the FC above 0.5 and I'd say fairly consistently after 24 hours it's back to that or less.

Assuming CYA is actually 70 (I honestly don't know if it is... I can do that Taylor K-2006C CYA three times in a row and get three very different answers), according to the SLAM calculator and the PoolMath calculator, to SLAM the pool will require 28ppm FC? It sounds like this all comes down to CYA level - where the difference between say 50 and 70 is the difference between needing 20ppm and 28ppm (which is 3 1/2 vs 5 gallons).

Bottom line, that's 5 gallons of 10% chlorine per day, for some unknown number of days or weeks, and if that doesn't work, I have to drain the pool? Are there any other possible tests to determine what else could be wrong?

 

[BDY]

If I read the above correctly your last test was from 8pm to 12pm? Depending on when sun went down that could still have been UV on the FC. Have you done a full OCLT?
Overnight Chlorine Loss Test

From dark to as near sunrise as you can force yourself to wake up? If the criteria fails then regardless of it being a checmial or algae issue (or both) then something is eating the chlorine besides UV and the SLAM is the best way to get rid of it. It sounds like a mountain to climb but once over the top if you stay on the FC/CYA relationship you can be seasons or years without future issue.
FC/CYA Levels

If you pass the OCLT then maybe it’s just daily chlorine being consumed? Ohio is less UV strong than Texas but I lose 4-5ppm a day at 70 CYA right now, more if swimming parties. (I just raised to 80 and it is a noticeable difference in FC consumption but I did two OCLT first to make absolutely sure of no issues.

Just some thoughts…..

 

[proavia]

Your signarure indicates you have a "UV filter".
If you have a UV system, disable it as it can cause the FC to be used - which could compromise the OCLT and cause you to fail that critical test.
Figure out a way to disconnect the UV so you can run the pump without using the UV.

A residential sized UV system on an outdoor pool is basically worthless. That big orange ball in the sky supplies all the UV your pool needs - and then some. Permanently disconnecting it will also save you some electricity.

 

[FoolOfATook]

Hello everyone! I've been reading this forum for a while now and have learned a lot of great information, though I'm having a problem that I cannot seem to find an exact answer to.

TL;DR: History

I have a rectangular in-ground pool about 3 years old, approximately 18,000 gallons. This was installed by the previous owner and this is the second season for me. It is chlorine, has a sand filter, retractable cover, chlorinator and UV filter. We keep the pool covered nearly all of the time, opening it when we swim and closing it afterwards. Last year the pool was maintained bi-weekly by the company that installed it, and they opened and closed it for the seasons each time. I had been doing the general chemical maintenance and checking last in between their visits and didn't really have any issues. This year they informed me that they just don't have the resources to do pool maintenance visits and to find someone else. Given my experience last year I figured I could handle it in the meantime while I found someone else.

This year when they opened the pool at the beginning of May after being covered since end of September it was pretty murky and teal colored. They added an algicide and a lot of shock and said to give it a few days and should be fine. It seemed to clear up after a few days though given the cooler spring the water just wasn't warm enough to swim so it got very little use in May. I did periodically test it with my test strips from the previous season but was getting somewhat erratic results so just figured they were no longer good and needed new ones.

During a particularly rainy week we were out of town for about 5 days and when I came back the pool was back to being murky and teal again. The PSI on the filter was 23 (should be max 20) and when I backwashed it, it had a noticeable smell. Afterwards the PSI was back down to normal. Over the course of a few steps, I added the recommended amount of HTC algicide, shock and clarifier and waited. After a several days it began to slowly clear up, however that's when the problem really started...

The problem (finally)...

In short, the pool does not and will not hold chlorine. Over the course of the past three weeks I have probably added 20+ gallons of liquid (10%) and 2 maybe 3 containers of granulated. Consistently after about 4-6 hours the free chlorine was down to below 1, sometimes looking like 0. The CC seems to remain proportional to the FC where when one is high the other is high and when low they both are.

I continued to pour 4 to 5 gallons per day seeing the same results. We brought in a new pool company and they reported on the first visit that the pH was also very low (below their lowest measurement on their strips). I had seen this as well but was very inconsistent across the different types/brands of test strips I had used.

Intestingly, the water is crystal clear. Like... glass clear. You can see the bottom of the deep end almost as though there's no water in it. The pool company left in their notes that the water looks "awesome" and "extremely clear".

Recently I started to keep much more detailed notes, but assume unless otherwise I added at least 10ppm's worth of chlorine a day. Here's what I have in writing:

6/23: Pool company
Reported: pH < 6.2, FC < 0.5, Alkalinity ~ 80, CYA 0 (This would have been after I had added 1 or 2 gallons of liquid chlorine earlier that day).
Added: 2 gal shock, 1 lb pH plus

6/29: Pool company
Reported: ph < 6.2, FC < 0.5, Alkalinity ~ 80, CYA 0 (same exactly as last time)
Added: 2lbs "yellow out", 1 lb ph plus, 2 gal shock, 1lb CYA.

6/30: Added 4 lbs ph plus. After several hours the pH was still below scale on test strips.

(Finally purchased a Taylor K-2006 kit so started using it)

7/1: 1:30pm
pH < 6.8 (bottom of scale) took 17 drops of R0006 to get to pH 7.4. According to book that means ~10 lbs of pH up should be added.
FAS-DPD: 2 drops to colorless (0.4ppm FC), +5 drops to pink again, 5-6 drops to colorless again (1.0-1.2ppm CC).
CYA: approx 90 (not 100% sure what it means by "black dot 'just barely' disappears" though).
+ 2 gal 10% liquid chlorine

7/1 7:30pm
Test strip: pH ~6.4, CC ~3, FC ~3-5.
TA: 13 drops = 130 ?
Added: 4 lbs pH up

7/2 9:00am
pH: ~7.2
FAS-DPD: 2 drops to colorless (0.4ppm FC), 2 drops to pink again (0.8ppm CC)
Added: 4 lbs pH up

7/2 11:00am
Added: 1 gal 10%
pH: ~7.5

7/2 1:30pm
pH: ~7.4
FAS-DPD: 7.5 ppm FC, 1.0 ppm CC (at this point I felt like some progress because it was the longest I'd ever seen it hold chlorine).

7/2 3pm: small pool party, 3 swimmers for about an hour.

7/3 9:30am
ph: ~7.4
Test strip: FC/TC off scale low.
TA: 80-120
Added: 1 gal 10% liquid
Noted water level was at 1/3 skimmer height so added about 45 mins from hose and now up to just over 1/2 skimmer height.

Summary

While the pH seems to be holding steady still seeing chlorine fall. We have had relatively little swimming this season and this chlorine will fall regardless of whether or not anyone goes in so I don't think it's swimmer contamination. Also, the pool is covered nearly 24/7 so it isn't contaminated by rain, nor does it receive UV light. Chlorine also drops down over night. Being that I didn't feel confident in the results from the test strips I was reluctant to add additional stabilizer in case lock was a problem. Recent tests with the Taylor show it to be in the 70-90 range now. I wouldn't also say we've seen "excessive heat" yet this summer - hottest day might have been 89 degrees and there have been quite a few cool days too. Finally, since the water seems so perhaps not an algae issue... unless there are 100% perfectly clear algae? The only thing I haven't formally done is a "SLAM", though I have been adding 3-4 gallons (or granule equivalent) per day.

Help!

Anyway... extremely long story short. What could this be, and what else should I do? I mean, the pool is very clear and comfortable to swim in, it's just that it seems that I have to continue to add a gallon of chlorine every 4-6 hours to keep it above 0.5.

Thanks (and sorry for the super long message).

FK

Do you know what your CYA is right now? SWG is different values than my pool but If you’ve had tabs in for a long time or the companies used a lot of granular shock that can increase CYA. I had to go to a pool store to get an accurate CYA test and scale my chlorine additions appropriately. Once you have a test with values you can plug them into TFPs pool math app and it will tell you how much to add. I also found the articles in the Algae section of PoolSchool helpful, but the PoolMath app will scale your needed FC for you so you don’t have to guess or waste money on not putting enough in and having to do it again.

 

[kimkats]

They reported their CYA as 70=/-. Please do not take your water to the pool store for CYA testing or any testing really. The CYA test is the one they get wrong the most

To the OP-you are correct that CYA and FC go hand in hand. Here is quick chart to show you:

FC vs CYA chart location

Can anyone point me to the fc cya chart that used to be here somewhere? Had link buy changed ohones, link list. Now cannot find chart. Was green I think. Thank you.

www.troublefreepool.com

And here it the page to show you the hows and whys of the relationship between the two:
FC/CYA Levels

Trust the SLAM process. The more you test and add FC the faster your pool will clear.

 

[drsipe]

So, I've been pouring in a gallon a day just to keep the FC above 0.5 and I'd say fairly consistently after 24 hours it's back to that or less.

Assuming CYA is actually 70 (I honestly don't know if it is... I can do that Taylor K-2006C CYA three times in a row and get three very different answers), according to the SLAM calculator and the PoolMath calculator, to SLAM the pool will require 28ppm FC? It sounds like this all comes down to CYA level - where the difference between say 50 and 70 is the difference between needing 20ppm and 28ppm (which is 3 1/2 vs 5 gallons).

Bottom line, that's 5 gallons of 10% chlorine per day, for some unknown number of days or weeks, and if that doesn't work, I have to drain the pool? Are there any other possible tests to determine what else could be wrong?

Your pool doesn't hate chlorine, it is loving to eat the chlorine.

Pools eat chlorine for a few reasons:
1. You have biologicals in the water, this could be bacteria, virus or algae.
2. You don't have enough CYA to protect your chlorine from UV light (as stated in another post, you should turn off your UV "filter"). With your test results of 90 for CYA, your on the high side so, I don't think it's low CYA and natural UV that is eating your chlorine.
3. Some of the "magic potions" from the pool stores can cause the chlorine to drop as the chlorine oxidizes the potion.

You can turn off the UV "filter" and see if that helps, but you may need a SLAM, to confirm that a SLAM is needed, perform an overnight chlorine loss test (without the UV "filter" on). If you fail an overnight chlorine test, a SLAM is needed, and before you can perform a SLAM, you will need to lower the CYA. The only way to lower CYA is partial drain and refill.

Perform the Overnight FC Loss Test (OCLT)

The Overnight Chlorine Loss Test tells if the SLAM is finished or if you need to start a SLAM. This article says how to do the OCLT.

www.troublefreepool.com

Draining - Further Reading

www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.

www.troublefreepool.com

 

[V___25]

Just getting caught up on this but are you maintaining the pool or is a pool company? TFP methods and pool maintenance company methods do not mix. Trust your results from your test kit and not theirs.
Guess strips are horribly inaccurate for CYA readings. I used the first summer we bought the house and it said my CYA was 0 when it was around 90-100.

 

[FrankieKat]

Just getting caught up on this but are you maintaining the pool or is a pool company? TFP methods and pool maintenance company methods do not mix. Trust your results from your test kit and not theirs.
Guess strips are horribly inaccurate for CYA readings. I used the first summer we bought the house and it said my CYA was 0 when it was around 90-100.

It's me (apparently). I brought on this pool company only 3 or 4 weeks ago thinking they would help but it's pretty clear they aren't (though at coming once a week I can't see that they're doing much harm either).

Your pool doesn't hate chlorine, it is loving to eat the chlorine.

Haha. I meant, it hates it so much it gets rid of it as soon as I put it in there!

Pools eat chlorine for a few reasons:
1. You have biologicals in the water, this could be bacteria, virus or algae.
2. You don't have enough CYA to protect your chlorine from UV light (as stated in another post, you should turn off your UV "filter"). With your test results of 90 for CYA, your on the high side so, I don't think it's low CYA and natural UV that is eating your chlorine.
3. Some of the "magic potions" from the pool stores can cause the chlorine to drop as the chlorine oxidizes the potion.

You can turn off the UV "filter" and see if that helps, but you may need a SLAM, to confirm that a SLAM is needed, perform an overnight chlorine loss test (without the UV "filter" on). If you fail an overnight chlorine test, a SLAM is needed, and before you can perform a SLAM, you will need to lower the CYA. The only way to lower CYA is partial drain and refill.

Pretty clear at this point I'm going to need to do an extended SLAM or a drain. In terms of overnight chlorine test, this problem has been pretty consistent for at least a month now which is just that no matter how much chlorine I put in, it is gone within 24-36 hours. I've been pouring in one, sometimes two gallons of 10% daily and sometimes also adding 9oz or so of granules just for good measure and pretty consistently when I test it the next day I've got 0.2-0.4 FC and around 0.4 CC. Nothing me or any pool company has done has made any difference in how this is happening. On Sunday night the water was glass clear from 7ft down, and when I opened it up today I couldn't see the bottom.

I am still having a lot of trouble interpreting the Taylor CYA test, so I'm not really sure where to start, but if I took an average and went with 80 I'll be adding 5 1/2 gallons a day, and this has to be liquid, not granules correct? Just wondering if there's anything cheaper than $50/day of liquid. Guess I'll be heading out to all of the pool stores tomorrow and buying them all out!

Thanks everyone!

FK

 

[drsipe]

Pretty clear at this point I'm going to need to do an extended SLAM or a drain. In terms of overnight chlorine test, this problem has been pretty consistent for at least a month now which is just that no matter how much chlorine I put in, it is gone within 24-36 hours. I've been pouring in one, sometimes two gallons of 10% daily and sometimes also adding 9oz or so of granules just for good measure and pretty consistently when I test it the next day I've got 0.2-0.4 FC and around 0.4 CC. Nothing me or any pool company has done has made any difference in how this is happening. On Sunday night the water was glass clear from 7ft down, and when I opened it up today I couldn't see the bottom.

It does appear that a SLAM is needed, but before you can perform a SLAM, you need to get the CYA levels down, which means a partial drain and fill or several partial drain and fills.

If you try to perform a SLAM at 90 CYA you would need a FC level of 39 ppm, which is unrealistic to achieve. You need to get down to a CYA level of 30-40, so that your SLAM chlorine levels are realistic.

 

[FrankieKat]

It does appear that a SLAM is needed, but before you can perform a SLAM, you need to get the CYA levels down, which means a partial drain and fill or several partial drain and fills.

If you try to perform a SLAM at 90 CYA you would need a FC level of 39 ppm, which is unrealistic to achieve. You need to get down to a CYA level of 30-40, so that your SLAM chlorine levels are realistic.

View attachment 513323

That makes sense... 5-6 gallons a day seemed pretty crazy to me. Regardless I'm going to hit the stores that are open tonight and buy as much as I can.

Just tested CYA, it's between 50-80 so I'll read up on partially draining my pool first.

 

[kimkats]

Make sure to check the date codes on the chlorine. You don't want it to be older than 3 months. Chlorine does degrade over time.

 

[Mdragger88]

Just tested CYA, it's between 50-80 so I'll read up on partially draining my pool first.

You want to do the cya test in bright light- preferably outdoors on a sunny day.
Follow the steps listed here

CYA - Cyanuric Acid Test

Cyanuric Acid (CYA) is the chemical name for what is commonly referred to as Stabilizer … Read more…

www.troublefreepool.com

 

[RLP]

When you are doing the cya test, you can pour the contents from the test tube back into the mixing bottle, and repeat the test multiple times with the same sample. This will help you "practice" until you start to get consistent results.

You kind of have to be nonchalant about it. If you focus in on it, you'll drive yourself nuts.

Pour it from the red tipped bottle into the test tube, glance at the dot, then look away, then glance again. When it appears to be mostly obscure, stop there. I find that it never really completely goes away, or if it does, it kind of comes back after a few seconds.

 

[FrankieKat]

Make sure to check the date codes on the chlorine. You don't want it to be older than 3 months. Chlorine does degrade over time.

Yeah... I do try to and get the highest numbers... they don't put actual dates on the "Pool Essentials Chlorinating Liquid" I usually get from Wal-Mart (it's by far the least expensive and close by).

When you are doing the cya test, you can pour the contents from the test tube back into the mixing bottle, and repeat the test multiple times with the same sample. This will help you "practice" until you start to get consistent results.

You kind of have to be nonchalant about it. If you focus in on it, you'll drive yourself nuts.

Pour it from the red tipped bottle into the test tube, glance at the dot, then look away, then glance again. When it appears to be mostly obscure, stop there. I find that it never really completely goes away, or if it does, it kind of comes back after a few seconds.

"Drive yourself nuts" - that's a good way to put it! lol I do have a hard time trying to judge what "the dot just 'barely disappears' means". Is it when you start to see it become difficult to see but if you squint or hold it in the light differently, you can see it? Or when you can focus and see the dot only because you know it's there and are looking for it? Or when, no matter how hard you look there's no dot? I've asked my wife to look too and she always comes up with a different number than me. I've repeated pouring it back in outside 4 or 5 times right in a row and somehow I get wildly different numbers each time! (d'oh!).

I'm targeting 25 ppm for the SLAM just to try and split the difference. With the Taylor would it be a valid result to use 5mL of water and count each drop as 1ppm? Just trying to avoid using 50-60 drops to check the SLAM level each time. If so, would I still use 2 scoops of the R-0870?

One question... could having a retractable cover possibly contribute to this? As in, could it be that whatever is contaminating the pool is actually living in/on the cover itself?

Thanks again everyone!

FK

 

[FrankieKat]

SLAM LOG

7/13 7:30 PM:

• FAS-DSD (25mL): ~0.4-0.6 FC, 0.2-0.4
• CYA: 50-80 (out of CYA... re-ordered but won't arrive until Tues)
• + 2 gallons 10% liquid and ~27 oz 52% hypochlorite granules (+ ~17ppm FC)
• Current SLAM level: 17.5
• Restarted S200 longest cycle

7/13 9:30 PM:

• + 1 gallon 10% liquid and ~18 oz 52% hypochlorite granules (+ ~10ppm FC)
• Current SLAM level: 27 ** calculated
• Restarted S200 longest cycle

7/14 7:30 AM:

• + 1 gallon 10% liquid and ~27 oz 52% hypochlorite granules (+ ~12ppm FC)
• Current SLAM level: 39 ** calculated
• Noticeable improvement in clarity
• Left cover open overnight
• Restarted S200 longest cycle

7/14 11:15 AM:

• Weather warm (high of 91 today) and direct sun. Cover still open.
• FAS-DSD (10mL): 19-20 FC, ~0.5-1 CC
• Chlorine previously added: 39ppm - 20ppm = lost 19ppm over 16 hours.
• + 1 gallon 10% liquid and ~27 oz 52% hypochlorite granules (+ ~12ppm FC)
• Current SLAM level: 31
• Restarted S200 longest cycle

7/14 2:15 PM:

• Weather hot - 91 degrees F and full direct sun. Cover still open.
• FAS-DSD (10mL): 25 FC, ~0.5-1 CC
• Chlorine previously added: 31ppm - 25ppm = lost 6ppm over 3 hours.
• + 1 gallon 10% liquid (+ 5.6pm FC)
• Current SLAM level: 30

 

[RLP]

"Drive yourself nuts" - that's a good way to put it! lol I do have a hard time trying to judge what "the dot just 'barely disappears' means". Is it when you start to see it become difficult to see but if you squint or hold it in the light diffe Or when you can focus and see the dot only because you know it's there and are looking for it? Or when, no matter how hard you look there's no dot? I've asked my wife to look too and she always comes up with a different number than me. I've repeated pouring it back in outside 4 or 5 times right in a row and somehow I get wildly different numbers each time! (d'oh!).

Other members fill the test vial to the 1st line (100), (looking through the side of the vial at the scale) then do the glance. If the dot is still visible, look through the side again, fill to the next line. Then glance down the tube. Still Visible? Fill to the next line, then do the glance. And so on.

In other words, dont look down the tube while you are pouring, pour to a line then look down the tube.

Its best to be outside with your back to the sun.

I'm targeting 25 ppm for the SLAM just to try and split the difference. With the Taylor would it be a valid result to use 5mL of water and count each drop as 1ppm?

Yes, its just not as accurate.

Just trying to avoid using 50-60 drops to check the SLAM level each time. If so, would I still use 2 scoops of the R-0870?

One flat scoop or a little less is plenty.

I use one heaping scoop and 10 ml sample for testing.

You want one or 2 grains of undisolved powder in the bottom of the vial after its all mixed.

Are you using a speed stir?

One question... could having a retractable cover possibly contribute to this? As in, could it be that whatever is contaminating the pool is actually living in/on the cover itself?

Yes, it has been reported that the underside of an autocover could harbor algae. Check it.

Also, Keep the cover open while doing the slam.

Thanks again everyone!

FK

 

[JupiterFL]

"Drive yourself nuts" - that's a good way to put it!

R-7065 CYA Standard 50ppm (2oz)

tftestkits.net

This is a standard solution at 50ppm that you could order to see exactly what 50ppm looks like.

 

[JupiterFL]

There are instructions that you can find on the fourm.

 

[FrankieKat]

Yes, it has been reported that the underside of an autocover could harbor algae. Check it.

Also, Keep the cover open while doing the slam.

Oh great... I was hoping the answer was no! So I would expect to visually see algae if it were a significant problem? I guess the only way to do that would be to open it halfway and swim under it - it's the kind that rests on top of the water to some extent so always in contact.

Perhaps if I just leave the autocover open and dry for a long period of time that will kill it off?

I should also add, the one thing regarding algae is that I've never actually seen any color to the pool other than cloudy - I've never green, yellow or black or anything nor have I ever seen anything that even looks like something alive. Compare this image from Thursday to the one from 4 days earlier. That gives a good indication of what it really looks like.

 

[FrankieKat]

Yes, its just not as accurate.

I guess I'm just trying to gauge rougher numbers in the beginning - did it drop 5 or 10ppm - and save my drops!

One flat scoop or a little less is plenty.

I use one heaping scoop and 10 ml sample for testing.

You want one or 2 grains of undisolved powder in the bottom of the vial after its all mixed.

Are you using a speed stir?

I am not... just swirling the vials.