Mysterious chlorine loss... SLAM even though not failing entrance criteria?

Mdragger88

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@triangleman3 I hate to see it dragging on for you - are u sure u got all the crannies 🤷‍♀️ - the overnight chlorine loss test results are pointing to something hidden somewhere, somehow. Ladder cups/ bumpers perhaps? Are you certain of your cya level? Just spit balling here…
 
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Newdude

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Jun 16, 2019
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Thoughts?

I always have thoughts!!!! Like this one. And you agree with me too👇
Don't you see I'm looking for the easy way out?!
:laughblue:

But seriously though. If you are OK with the risks of losing ground in the battle, you are free to do whatever you wish in your pool. Maybe it works and just takes longer with no real loss having clear water. It's possible but not guaranteed, so we can't reccomend it as a usual thing. And even if it worked for some, it wouldn't be repeatable for everyone.

And I TOTALLY hear what you are saying about the preaching of adding 5 ppm a day while waiting for the test kit. It's kind of misleading because you've seen firsthand how little that will do with a swamp. It's not so much a 'stop the growth' amount so much as it's a stop it from getting exponentially out of control amount. And without knowing all those newb's CYA, it's fairly guaranteed to be a safe amount added for them. So there has to be a happy medium # picked and it's 5 ppm. It's far from a miracle #.
 

TriangleMan

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May 30, 2021
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are u sure u got all the crannies 🤷‍♀️

I'm questioning a lot of what I'm doing at this point. I'm trying to be diligent, but real life does get in the way. While I started strong, the scrubbing and manually vacuuming every day is hard to keep up in my active house, which no doubt is contributing to it dragging on. I at least go for every other day (e.g. brush today, vacuum tomorrow), while maintaining chlorine levels throughout the day (while I still have the luxury of working from home). I'm crossing my fingers that since I'm on the tail end of the process with clear water, it's not as critical and the chlorine will eventually win... that may not be a good gamble... At the very least I hope to cost-effectively buy time until the weekend when I have time to be more thorough.

While I have been doing the perfectly upside down, slow drip approach to adding reagant, I do think I've been allowing the powder to get contaminated on the scooper, though, potentially throwing off my FC levels (I don't personally think that 3.5ppm loss a couple nights ago was real).

I'm also pretty confident at this point, though, that the black stuff that was gathering in the skimmers at the water line is just plain dirt. It's quite windy in my backyard, due to neighborhood geography, and there is a lot of patchy places in the lawn where the new grass simply hasn't grown in (thanks again drought!) leaving exposed dirt.

All signs point to imminent success that I just haven't quite reached... That's why I'm acknowledging that it may take a while given my now less than perfect cleaning regimen, and searching for a cost-effective way if it must drag on... More on that in my next post.

I always have thoughts!!!! Like this one. And you agree with me too👇

Yep, still no argument there! Still looking for the easy way out! :LOL: But I'm also putting in as much of the effort and hard work as I can muster until I find it! Everything you guys say makes great sense, and I concede that I have not successfully disputed any of it, so I'm still following the plan as best I can!

I do still very much appreciate all of the advice and continued willingness to provide recommendations!
 

Saturn94

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Thanks Bperry! I do love our paradise in the backyard!

Update: I drained the ladder and a whole ton of stuff came out. I'd describe it as if the people who opened the pool must have put a half bag of dichlor or cal-hypo down each side. (Maybe not a bad idea??)

I'm convinced I'll need to open up the niche at the next opportunity.

Also, there was this black gooey crud at the water line in the skimmers this morning... Any idea what that could be? Just want to make sure the high chlorine levels aren't taking off a protective film from the liner or something... (The brown discoloration below the water line is from the high alkalinity fill water from the well)

View attachment 345959

The black gooey stuff is likely sunscreen. I see the same thing in our pool if anyone with a bunch of sunscreen on gets in. I’ve only seen it appear with the introduction of sunscreen in the water.
 
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Newdude

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I'm questioning a lot of what I'm doing at this point. I'm trying to be diligent, but real life does get in the way.
We all get it. We do. Everybody is gung-ho for a weekend, some for a week+, but after that ?? Well the real world has to take precedence at some point. Especially this time of year with kids and the 57 end of the year celebrations from 6th grade, dance, scouts, baseball, etc etc etc. And work. And yeah. We get it.

We advise everyone to do the best they can. If some things take some attention away from the battle, the battle takes a bit longer and the world keeps turning. You've done awesome. You're still doing awsome.
 

TriangleMan

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May 30, 2021
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I think most people try and top up the chlorine 3-4 times per day. Of course more is better. I’m not sure the amount of chlorine is any different in the end, but would be interested to hear if so.

Ok... so I've been thinking about the math behind adding chlorine throughout the day vs letting it drift to FC/CYA levels and then raising back to SLAM at night when the sun is not your nemesis. In the end, I think I've convinced myself that there's not a lot to be gained.

Disclaimer: What follows is based on mathematical inference, not actually science of chlorine loss or the effects of UV, etc.... I'm no @chem geek !

It seems like a reasonable assumption for chlorine loss to the sun is something like 5% of FC per hour based on what I've read around here -- i.e. FC(t) = 0.95*FC(t-1). For a 25000 gal pool, at CYA = 50 and FC = 8, that equates to roughly 4.5ppm over the course of 16 hours. (8-8*0.95^16) That seems to be in keeping with the anecdotes here.

Using that same logic, then, starting at SLAM level 20, if I just let the sun do its thing for 16 hours, I end up at FC = 20*0.95^16 = 8.8 for a loss of 11.2ppm.

(For you math purists, I brushed up on my calculus a little: FC remaining at hour 't' = f(t) = FC*0.95^t ==> chlorine lost at the end of hour t = CL(t) = 0.05*f(t) = FC*0.05*0.95^t ==> chlorine lost over 16 hours = Integral_from0to15(CL(t))dt = FC*0.05*(0.95^15-1)/ln(0.95) = 10.46 ppm... so let's just go with the discrete method and say 11.2ppm is close enough!)

Compare that with dosing every hour to return to FC=20, which means I'm losing a constant 0.05*20 per hour for 16 hours ==> 0.05*20*16 = a loss of 16 ppm.

At face value, saving ~5 ppm = 1 gal of 12.5% bleach sounds like it may be a good idea... however if the algae is able to consume 2ppm over 8 hours at night, then figure it's good for at least 4ppm over 16 hours during the day. That would take my FC down to (20 - 11.2 - 4) = 4.8ppm, which may be too low for comfort if I don't want the algae to continue growing, which experience has shown it can even if FC is maintained at the high end of the normal FC/CYA range.

Ok then, add 5ppm at the start of the day to keep maintenance effort low but provide a buffer, so I start at 25 ppm, lose 14ppm (alright, 13.07 ppm if you really must) and end at a safer 11ppm. (7 after algae)
My intent would always be to start the night hours at the full SLAM level, so returning to 20ppm means adding back in the 9, plus the 4 that I'm assuming the algae will continue to consume during the day, yields a total addition of 5 + 9 + 4= 18 ppm with this approach.

Contrast that with adding 1ppm per hour for 16 hours if following TFP methods as aggressively as possible, and still assuming I lose 4 ppm to algae ==> 16 + 4 = 20ppm.

The "lazy" approach nets me a grand total savings of 2 ppm (half a gallon of 10% bleach... so $2-$3?).

Thus... it's not really saving money... although there's a decent argument to make that it's saving time and effort throughout the day, at the cost of increased risk of algae growth if the algae is still strong enough to be much more aggressive than 4ppm per day if left unmonitored. Again... this might only be even worth considering at the very tail end of the SLAM when such a bet that the algae is nearly beaten is safer... but it's still a gamble.

So.... the moral of the story is to keep following the TFP way, but don't stress as much if you can't hit the frequent small additions and opt for a few lesser but bigger additions?

Apologies for the long post... Hopefully my math is right. I'm sure people smarter than I will happily poke holes in it. Have at it!
 
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TexEdmond

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Thoughts?

Man, I'm so sorry you're having to deal with this. The lazy dude / macguyver in me wishes there was some kind of "portable intellichem" device that would dose the pool at regular intervals so there could be more time for ... Y'know, life.

I know it doesn't affect everyone, but I've thought about asking why SWCG pools turn the generator to 0% instead of 100%. I'm sure there's good reasons behind it. I just had the realization that the SWCG I'm fixing to install on the pool will save me upwards of $4 per day in bleach, plus the time to drive to the hardware store to pick it up.

Of course I wouldn't know the finer points of a SLAM until I have to do one. Is there an upper limit you have to stay under, or do you just go scorched earth on the thing?
 
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TexEdmond

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It's not so much a 'stop the growth' amount so much as it's a stop it from getting exponentially out of control amount.

I don't intend to speak for triangleman, but I certainly would like to make the observation that in this (anecdotal) instance, he's adding WAY more chlorine than this to effectively the same result... He's just on the flat side of the asymptote of that exponential growth.
 

TriangleMan

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May 30, 2021
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OCLT: FC: 20 ppm to 17.5 ppm. CC: 0

After having added 17.5 ppm during the preceding day over the course of three additions, it's difficult to rationalize how I could be going backwards. I did not brush yesterday, but if the algae can multiply still at FC=20 then something's amiss (the lowest it got to before chlorine addition was 12). If anything, my CYA is actually much closer to 40 than it is 50, so I wouldn't say I'm undershooting FC.

The pool looks great and it's hard to say all this effort is worth it. All the chlorine I've dumped into a clear pool I could just have saved for the next time it turned cloudy.

I have a tough decision to continue down this path and go spend another $100 on chlorine to get me through the weekend, or just revert to the FC/CYA level and deal with a yo-yo cycle of clear to cloudy to clear. At those FC levels, as I understand it, at least the dangerous bacteria is still dead.

(It'll also give me a chance to check and correct pH which I fear has gotten very high from rain, well water, and aeration. My kids have been complaining that their eyesight is clouding up after swimming. Also CSI is very high.)

Again, the pool is crystal clear, and has been for two weeks going back to the start of this thread. Is this amount of SLAM effort typical?
 
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TriangleMan

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May 30, 2021
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Is there an upper limit you have to stay under, or do you just go scorched earth on the thing?

I haven't seen a clear answer on this. I'm willing (and interested!) to go above 'safe' swimming levels at night if it means the algae dies faster, as long as it's still safe for the liner and equipment.

So far, I've only seen to stay at safe-swimming SLAM levels of 40% of CYA.
 

Bperry

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Aug 20, 2020
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I haven't seen a clear answer on this. I'm willing (and interested!) to go above 'safe' swimming levels at night if it means the algae dies faster, as long as it's still safe for the liner and equipment.

So far, I've only seen to stay at safe-swimming SLAM levels of 40% of CYA.
Curious if you are taking the water samples from ~18” below the surface in the same location every time? Also not near a return jet? Just wondering if test variation might be the cause.
 

TriangleMan

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Curious if you are taking the water samples from ~18” below the surface in the same location every time?
Happy to provide as much info as I can:
Same way every time. Elbow depth in the middle of the long (40') side opposite the two skimmers, halfway between two returns.

It's likely to be a lower circulation point in the pool because of its distance from the returns and being opposite the side with the skimmers where everything is funneled to.

Also, I have all returns (four total, including two on the steps) aimed upwards to disturb the surface and ensure debris heads to the skimmer. I almost never have to skim anything out myself, unless it's very high wind.
 
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Bperry

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Happy to provide as much info as I can:
Same way every time. Elbow depth in the middle of the long (40') side opposite the two skimmers, halfway between two returns.

It's likely to be a lower circulation point in the pool because of its distance from the returns and being opposite the side with the skimmers where everything is funneled to.

Also, I have all returns (four total, including two on the steps) aimed upwards to disturb the surface and ensure debris heads to the skimmer. I almost never have to skim anything out myself, unless it's very high wind.
Sounds like the right plan. It might be interesting to test in another spot as well to compare but that’s just grasping for ideas on what’s going on.

Also, have you heard the trick here about avoiding having to stick your arm in the water to get a sample? I use a thin pvc pipe ~24” long with the ends capped and a 1/4” hole drilled in each end. Just dip the pipe in the water and cover the hole with a finger and then lift the pipe out of the water and over a container. Then let your finger off the cap and the water fills your container for testing.
 
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TriangleMan

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The black gooey stuff is likely sunscreen. I see the same thing in our pool if anyone with a bunch of sunscreen on gets in. I’ve only seen it appear with the introduction of sunscreen in the water.

That makes a lot of sense. It could very easily be a mix of dirt + sunscreen.

In fact, my wife ensures our kids (ages 3, 6, and 8) are never in the pool without a healthy layer of the stuff (sunscreen, not dirt... They handle the additional layer of dirt just fine on their own).

I imagine that stuff is hard to break down, and I recall reading on here that it does consume chlorine. The pool is also well used! Could that be what the chlorine is working on at night??
 
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TriangleMan

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That makes a lot of sense. It could very easily be a mix of dirt + sunscreen.
...
Could that be what the chlorine is working on at night??

Here's two days worth of black goo in the two skimmers (since I didn't brush yesterday), along with a swipe of goo (middle EDIT: bottom - definitely a slight color difference) on the concrete next to actual dirt from the grass. You can also see a layer of film & dirt floating in the skimmer.

It's worth noting that there is no sign of dead algae at the bottom of the pool.
 

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TriangleMan

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I threw some water on the dirt and goo samples to make sure the color difference isn't a result of being wet... A slight difference persists, although the dirt certainly gets darker.
The goo is also somewhat hydrophobic... it resists water on the ground from spreading into its area, and needs to be dripped from above. That's probably another indication of a sunscreen mix... not sure if it's true of algae itself.
 

TriangleMan

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Here's where my head is at:

I'm not a fan of throwing 3-4 gallons of bleach into a clear pool every day.
Going full circle all the way back to the beginning of this thread, I am not failing the /entrance/ criteria for a SLAM, according to this article.
"If you have algae, or the CC level is above 0.5, or the free chlorine (FC) level is zero, you should SLAM the pool."
1) I do not see algae (granted; I may still have it and not see it... but at this point I'm questioning that)
2) CC <= 0.5
3) FC > 0

On /at least/ two occasions, I've passed the /exit/ criteria as follows ("you are done when"):
1) CC is 0.5 or lower
2) I've passed on OCLT (overnight loss of 1ppm or less)
3) Water is clear

It is not stated explicitly in that article that failing a random OCLT warrants ENTRY into a SLAM. That's not one of the three criteria. If I've successfully destroyed the algae and maintained proper levels to keep it at bay, perhaps there is some other reason that the OCLT occasionally falters.

So then, I'm thinking of:
1) Returning to normal FC/CYA levels (FC=8 for CYA=50) and maintain it
-- I anticipate that means adding 1 gallon of chlorine to the pool daily rather than 3-4
2) Continuing to care for the pool with reasonable brushing, vacuuming, etc.
3) Monitor for cloudiness or CC>0.5

If I see cloudiness or register high levels of CC, I can use that to resume/restart a SLAM rather than continuing to linger in this indeterminate state.

"But Triangleman, failing an OCLT means there's something in the pool." Yes. Maybe it's algae, maybe it's sunscreen, maybe it's something else. If I do this and the algae blooms within a couple days, I guess I'll have my answer. At that point I'll resume 3-4 gallons of bleach a day, or whatever it takes to maintain FC=20. I wouldn't let the pool turn into a swamp, so it might be a setback, but it's information gained.

I know I'm not the first one to go down this road, and I know that there are plenty of stories of people ending the SLAM too soon, but the rigidity of the process is supposed to be because "it works for everyone." Maybe it did work.

Am I crazy? I'm sure this is not uncharted territory. I imagine you've seen cases like this over the years? I'm open to being talked out of it... but it's pretty enticing right now.
 

TexEdmond

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I have all returns (four total, including two on the steps) aimed upwards

I'm not an expert, but this is listed as the recommended method to raise pH without adding chemical. They say pH is unmeasurable during SLAM via chemical methods. I have read that high alkalinity and pH is the danger zone for algae growth, and that the more acidic the water, the more aggressive the chlorine treatment is.

I also seem to remember a post here reviewing 2 digital pH meters that do work at elevated chlorine levels, and when I saw one was only $15 or so, I bought one. This helped me take precise, repeated measurements before my TF100 arrived. I used it on my 7 gallon muriatic dump and it was a lifesaver.

I wonder what would happen if you could safely nudge your pH down, neutralize some alkalinity, maybe make it hostile enough to knock out the last of the algae (If it really is algae consuming your chlorine still)
 
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