Inorganic stains...ugh!

Jump to latest Follow Reply
I vacuumed another 400 gallons or so out. I am getting some light brown fluffy debris on the the pool floor, hard to say. Chlorine demand is coming down a bit, CYA has climbed up to 35. It should be closer to 50 by this time tomorrow.

pH has crept up to 7.4. I'm going to let it ride.

I scored some DE from a new pool store that I found. It took 4 cups to get the sand filter pressure up by 1 PSI. We'll see if this helps with water clarity or filtering metals out. The water is very clear already, but I am "that guy" who obsesses over water clarity at night by the pool light.

The liner still looks clear.
 
So there are a few things going on. I got the CYA up to 50. I am very confident in this measurement because I raised it from under 30 up to 50 in 10 ppm increments (5.5 lbs solid stabilizer total), and it tracked right where expected over the course of 5 days (it dissolved in a sock very quickly). However, the pool continued to suffer from extreme chlorine demand during the day. Overnight, it lost almost no chlorine (I tested it over the course of two nights and got the same result). But after sunrise, it was losing a bit over 1 ppm FC per hour, just burning through it. Is this to be expected? In any event, this seemed to "break" finally yesterday and the chlorine loss during the day is more typical. So that was odd.

So how white should I expect my stairs to remain? Around the time the chlorine demand broke, I noticed a bit of yellowing on my stairs (a Vitamin C tablet clears it right up again). I pulled the pH back down to 7.2 and added 3 oz sequestrant. The liner looks good, I don't see any stains. However there could be an overall darkening of liner that is occurring that you can't notice day by day (which is how I slowly got here in the first place). Any thoughts? Right now I'm just cleaning a white patch on the stairs and adding more sequestrant and checking it again each day. Am I right on the ragged edge of disaster here? I'd hate to lose any ground.
 
You are right in the thick of things trying to balance adequate FC against metals. That's a tough position. Now that summer is here, the natural thought is to increase CYA to protect the FC from the sun, but with that increased CYA comes a higher FC demand. So now you're finding yourself back in the position of being on that "borderline" of FC too high for the metals. The sequestrant is helping I'm sure, but has its limitations as well. When it gets to this point, it may be time for us to solicit the help of another set of eyes to review your thread just to make sure we're not missing anything else important.
 
Yes I am in the thick of things! In my case there seem to be so many mysteries and contradictions with this process:

1) Why did the CA/AA/MF treatment caused increased chlorine demand during daylight hours only (1 PPM/hour) with a healthy CYA level of 50? Zero loss at night.
2) The AA instructions mention that the pH will tend to get pulled lower. Over only six days, mine floated from 7.2 to 7.7!
3) After the CA/AA/MF treatment and 15% water replacement and less than 48 hours of low chlorine, my CYA crashed from 45 to 15 (a 66% loss!)
 
Part of the battle will be keeping your pH low and keeping FC under 5. You may have changed most of the water over since stopping algaecide but that copper that was on the liner is now in the water. Somewhere around 72hrs after AA treatment was where I saw FC consumption taper off
 
Two more:

4) Why is it that CYA reduces the rate at which chlorine oxidizes organics, but not AA/CA? Why wouldn't the higher CYA level allow you to have a higher FC level without interfering with the AA/CA treatment?
5) Once the liner is nice and clear, why can't you go ahead and SLAM the remaining AA/CA? I'm still unclear as to what the remaining 1-2 week process that I am waiting for is.

Another observation: I think today when the stairs started to yellow a bit, there was a bit of a blue-green hue to the water. Subtle but there. Note that I've been religiously keeping the FC inline with my CYA (4-8), and have algecide still active in the pool. So it is not algae. Is that copper starting to precipitate? When I pulled the pH down to 7.2 and hit it with 4 more ounces of sequestrant, it seems like it is back to the nice light blue. Note that I feel the liner color imparts a hue to the water, so the liner color affects the observed water color. But looking directly at the liner, it still looks like the same nice light blue.
 
I have seen that green hue in the water get fixed by just adding sequestrant. Like you, it wasn't algea, the water was perfectly clear, just had a green tint. I've only had that happen once. But like I said, shortly after adding sequestrant, it went away.

Sent from my SM-G900V using Tapatalk
 
Good morning. you mentioned using Metal Free specifically as your sequestrant.

Metal Free by Natural chemistry is NOT an HEDP type sequestrant...you need to immediately get a startup dose of HEDP type sequestrant such as Metal Magic by proteam or jacks Magic in there or I fear you risk the return of the stains.

Also worth noting -- Metal Free is citric acid, which will also cause increased chlorine demand, so there's that mystery unravelled ;)

Once you have a phosphonic sequestrant added, you will also need to add periodic maintenance doses.

Hope that helps preserve your hard work.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Thanks for the post Swampwoman. I am aware of the advantages of HEDP as well as the increased chlorine demand from CA. The Jack's Magic is backordered and I won't have it until late next week. So I'm trying to hum along with what I've got to work with. I don't think you actually unraveled any of my Five Contradictions and Mysteries. I'll post them again here if you'd be so kind as to dig into any of them:

1) Why did the CA/AA/MF treatment caused increased chlorine demand during daylight hours only (1 PPM/hour) with a healthy CYA level of 50? Zero loss at night.
2) The AA instructions mention that the pH will tend to get pulled lower. Over only six days, mine floated from 7.2 to 7.7!
3) After the CA/AA/MF treatment and 15% water replacement and less than 48 hours of low chlorine, my CYA crashed from 45 to 15 (a 66% loss!)
4) Why is it that CYA reduces the rate at which chlorine oxidizes organics, but not AA/CA? Why wouldn't the higher CYA level allow you to have a higher FC level without interfering with the AA/CA treatment?
5) Once the liner is nice and clear, why can't you go ahead and SLAM the remaining AA/CA? I'm still unclear as to what the remaining 1-2 week process that I am waiting for is.

Thanks!
 
1 I have no explanation for this other than the sun must have some interaction with the AA. I don't recall seeing this reported previously.
2 AA is slightly acidic and tends to lower PH, your pool must have factors that contribute to PH rise that is stronger than the AA like high TA, aeration, high PH fill water, etc.
3 The most likely explanation is the low FC allowed bacteria to grow and consume the CYA.
4 CYA does not reduce the rate of oxidation of organics it reduces the rate that the sun oxidizes chlorine.
5 It is believed that raising FC too quickly will cause the stains to return. Higher FC will also oxidize the sequestrant faster. I'm not sure of the reasoning behind the 1-2 week wait either. It must have had some benefit to the writer.
 
Thanks pooldv. I do have a working hypothesis on #1. After my CYA plunged down to 15 or so, I raised it back up using the sock method mid week last week. So it hasn't been a week yet. So I guess it may have dissolved enough to escape the sock and register on the test, but not actually provide full UV protection yet? I guess it's irrelevant at this point as I am past that. At least until I have to repeat this whole process all over again...
 
It is always good to try to learn more stuff by discussing various experiences. That is a good theory on the CYA. It usually takes 24 hours after the CYA dissolves for it to fully register on the test. So, a day or two to dissolve and a day to fully mix in probably left FC more exposed to oxidation from the sun.
 
There seems to be a sixth mystery as well:

6) After the treatment, can you expect the metals to precipitate out such that they can be vacuumed out? The TFP consensus seems to be "no", which contradicts the sequestrant manufacturer instructions. Why the discrepancy?

So for #6, my answer seems to be "yes". I vacuumed to waste this morning, then hit the pool with 7 oz more of sequestrant as a result of the blue-green hue returning. The stairs were fairly white, the vinyl was at that point very clean, and the water has been crystal clear. After a few hours, the liner edges were covered in debris again. I've not seen debris form that quickly on a clear day before, so it seems to be metals. My sand filter has risen about 1 PSI in the past few days. So I guess that is progress.
 
5) Once the liner is nice and clear, why can't you go ahead and SLAM the remaining AA/CA? I'm still unclear as to what the remaining 1-2 week process that I am waiting for is.
Click to expand...

Re 5 - when you have metals, you want to entirely avoid Slamming if possible...preferably not just for a week (though the sequestrant instructions only say a week) but if possible, ever. That's because slamming causes oxidization of metals AND consumes/oxidizes the sequestrant as well.

Normally, if using AA specifically, you don't slam to get rid of extra...you keep bringing the FC up until it holds, but to a lower number than slam so that you don't oxidize the metal. Eg. I've added 5 ppm at a time and just continued every few hours til it held.

Regarding your other unexpected results/unintended consequences -- you are using a product with more citric acid in it, not an actual metal sequestrant. We can't predict its behavior because its just not really the same as an AA treatment as practiced/written up at TFP. So it does (apparently) make a difference on behavior/interactions compared to what we normally see happen after an AA treatment.

I'd put my money on the Metal Free as the cause of your other mysteries too ;) It might be worth contacting Natural Chemistry to see if adding cya while using their product is contraindicated.

If the Metal Free is the instruction telling you to "vacuum out" metal, then the mfg is attempting in essence to leverage the citric acid and its proprietary ingredients to actually cause a combine-and-floc/drop action. This also occurs more overtly with treatments like Alum, which is an actual floc.

Even Metal Magic believes some if the metal will filter out by combining with its HEDP sequestrant and calcium. Jacks believes this also -- I've spoken to their techs at length.

At the end of the day, it seems to me that while some combines and filters out, its a negligible amount and if the metal is in your source water, its pretty much a moot point. But a combo of sequestrant and pre-filtering can ultimately reduce the metal load and reduce the frequency of sequester maintenance doses.

So people aren't technically exactly correct when they say metal can't be filtered out, but in actual real world experience, for our purposes, its never really enough and its not reliable.

I've experimented (in a bucket) with Alum and on my raw well water, filtered out 1.6 ppm of 2 ppm. Then I tried the same test of my pool water (oxidized, then sequestered) and the floc didn't even develop ;) So there are many mysteries when it comes to metals, and many variables to control.

Said mysteries are exacerbated with various products in the mix. For example, I personally think your cya was sequestered/bonded right out before it was able to actually dissolve via the Metal Free, but I could be all wet on that, so to speak.

Out of all this the most important takeaway for practical purposes is to get some HEDP into the water as soon as possible because HEDP produces reliable results, or I predict your staining will return (as I've seen an cases with Metal Free where it does just that) and avoid slamming if possible.
 
Great thread, I am dealing with the same thing (iron stains). No well water, no old pipes. AA worked great but I can't get FC to come up. Treated 5 days ago, been adding 10 cups bleach per day.
C3- how much bleach did you use???
Thanks!!
 
Thanks SW, great info! Now it looks like the HEDP sequestrant may arrive this week, so I'll transition to that. I'll maintain with HEDP but I hope I don't have to run a 7.2 pH all summer. My pool really wants to pull up to 7.6 fairly quickly. It would take a lot of dry acid to keep it down there. I continue to vacuum out the precipitants to waste every morning and dilute it down further.

I am still having a noticeable amount of precipitation each day. But perhaps it is "negligible" in the grand scheme of things.

Flatlander, I probably burned through 6 gallons or more of 10% before it "broke". However in my case I had lowered/disabled/undissolved CYA going on.
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply