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Cya Testing And Shock Levels


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I received the TFTest kit this morning (Saturday delivery!) and I am really happy with it. I've had high CYA levels and haven't been able to measure above 5ppm, much less at teh shock levels my CYA level required.

So now I have a load of questions:

So far I've understood that CYA cannot be removed from pool water except if enough "biomass" (leaves, branches, dead cats, etc) gets in and converts the CYA to ammonia.

Last year when I closed the pool (with about 100 ppm CYA) I removed about 25% of the water. It was replaced with rainwater on the winter cover which included a large amount of biomass. Initial testing this year with my kit and at the pool store showed about 60 ppm CYA.

Over the past week I had a plumbing failure that prevented me from adding the bleach and circulating as normal, and the water got a bit cloudy (algae I believe). Since that event, multiple CYA testing showed between 15 and 30 CYA.

I should also mention that I added a heater and raised the pool temp from about 63°F to between 78°F and 85°.

Given these circumstances, could CYA be converted to ammonia this rapidly?

I am planning to ask the pool store to test for it but I'm not sure how well I would trust the results.

I had also asked in another forum if I could use my 5 ppm Taylor DPD test kit to measure higher levels of CL by diluting it with distilled water.

In the meantime I tried exactly that and got an even higher measurement with the sample mixed with 50% distilled water.

Any idea why this can happen? Is/was there something else affecting the CL measurement that got diluted by the distilled water?

Now that I can measure things I just shocked the pool. I knew I had some combined cl and wanted to fix it. After mixing the water well my results are:

Temp: 27.3°C/81.1°F (electronic meter

ORP: 696 (electronic meter)

pH: 7.56 (using electronic meter, confirmed with drop test)

Cl:18 ppm (love that test kit)

CCl: 1.5 " " " "

So how long should I expect to keep reading combined numbers?

.

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It's not biomass, but soil bacteria that can get into a pool that has no chlorine in it (usually over the winter if a pool is "let go") and can convert the CYA to ammonia. However, this doesn't always happen, is not controllable, and requires a LOT of chlorine to get rid of the ammonia and other intermediate products. Basically, the only practical way to lower CYA is by dilution of the water via partial drain/refill (or continuous drain/refill, but that uses more water).

Given your numbers for CYA, it is possible that bacteria did convert some of it to ammonia. It can happen in just a few days as happened to me this year when I stupidly didn't add chlorine mid-week as the pool warmed up (see this thread). However, since you are measuring FC, you've added enough chlorine to get rid of it (IF it converted at all).

As for the DPD chlorine test, it can bleach out above 10 ppm FC so you can certainly see the effect you saw where diluting the water results in a higher FC reading because the test isn't getting bleached out as much. This is one reason why the FAS-DPD test is better since it does not bleach out -- if you see a flash of pink when adding powder, just add more powder until you get the pink/red -- then add titrating reagent and count the drops (which are 0.2 or 0.5 ppm each, depending on sample size).

Since you are actually measuring a Free Chlorine (FC) level, you do not have any ammonia in your pool. Ammonia will not exist more than a few seconds to a minute or two in the presence of chlorine as it combines to form monochloramine very quickly. In your case, you are measuring some Combined Chlorine (CC), most likely due to the algae. Just shock the pool by keeping the FC at roughly 40% of the CYA level until 1) you measure <= 1 ppm FC drop overnight, 2) you measure <= 0.5 ppm CC and 3) the pool is crystal clear. See Defeating Algae for more details. The pool should clear and the CC drop within a few days since it doesn't sound like your algae bloom got very far -- for a big bloom it can take up to a week to clear the pool.

Richard

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Thanks again Richard, you're a star!

Just got back from the pool shop which is next to Kmart and Kroger and within those three stores I found the muriatic acid and borax I needed to introduce the borates.

I couldn't find any ammonia or borate testing kits at any of those locations but your answer saved me a trip to the fish store.

I also read almost the entire post - inlcuding the link to how CYA is metabolized - and found it highly informative. I agree that canning and selling the component - whichever one it is - that feeds on CYA would be a hot product. We could all go back to the tabs and erosion feeders and just add some of this stuff whenever we need to drop the CYA.

As I read through it I realized how that was almost exactly what I went through. Opening, warming the water, not checking the fc during a plumbing failure, milky but not green water, high cc - looks like this was pre-programmed. The only differences are that my pool is smaller and I think I caught it faster than you.

Pool shop just looked dumbfounded about the fc and cc levels - same test kit as my old one with a 5 ppm max. But they did get a cya of about 20 which lead me to purchase a floating puck feeder and gave me a use for that 50 lb bucket of tabs I still have left from my first visit to the pool store (a year ago).

I really love the TF test kit and you even addressed one question I had; how accurate does the spoonful need to be? From you answer I assume the amount of powder is not really critical, just as long as it turns pink. Is that correct? If I add two spoonfuls of powder it won't require double the amount of drops to determine accurate fc (or cc) level?

Also the powder seems to be partially granulate. Is that just the powder forming crystals or does the powder contain a desiccant?

After returning from shopping the numbers are:

Temp: 26.6°C

ORP: 588

fc: 5.0

cc: 0.5 (one drop cleared the slight tint)

pH: 7.28

TA: 110 measured by me and pool store, 310-370 by new test kit (problem here?)

CYA: < 20 measured with TF kit and pool store, my old kit showed ~30

optical clarity - about 95% (up from about 80% at worst phase)

Heading out now to get the borates in.

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You are correct that you just need to add enough powder to get a decent color. Any extra won't require more drops. Think of the powder as a dye (which it is) -- you need enough to see the color, but the dye is just indicating ANY presence of chlorine while the drops are removing chlorine so having more dye won't matter since it still won't show any pink if there is no chlorine left (because you've titrated it all away).

The powder does sometimes get granular so you want to keep the container capped. It will still work so long as it doesn't start turning a darker gray.

The ORP reading doesn't make sense since 5 ppm FC with 20 ppm CYA would read roughly around 700 mV though sensors vary -- it seems like yours needs to be better calibrated.

As for the TA, something seems wrong since I doubt that your TA is that high. If it were, then your pool would tend to rise in pH fairly quickly unless it were covered. Each drop represents 10 ppm. Perhaps you have static electricity on the tip and need to wipe it with a moist cloth or tissue (see this link). The drops should be well-formed and shouldn't squirt out like a stream. Compare with the other drops such as the FAS-DPD titrant -- they should be similar.

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Thanks for the dye explanation, makes a lot of sense.

I think the static buildup you mentioned explains a lot of things:

- The plastic case from the TF kit was very charged when I got it out of the shipping box.

- I first noticed fluctuating and jumping readings on the ORP/pH meter and slowly isolated them to being related how close I was to the container used to perform the test. The meter was stable when I was not touching it or the container but would start fluctuating as soon as my hand came within a few inches of it.

- I also noticed that the drops out of some of the reagent bottles would fly out of the tip at an angle and land on the sides of the test container. They also appeared to be smaller than I expected.

- I was having trouble getting reproducible & repeatable readings from the CYA and TA tests. I believe this was caused by the static buildup and that in turn made the ORP look wrong (reduced reagent, lower CYA value than real, ORP lower.) The ORP meter may also have been affected by the static buildup but I was sure I got a stable and repeatable reading before I recorded it. I've also found that pH has a drastic effect on the ORP with lower pH producing higher ORP values.

- I wiped the test kit case down and one of the bottles with a moist rag and that seemed to help stabilize things but I didn't think to wipe all the bottles and test beakers.

- The link you gave me about static on the test bottles will help for all future readings.

Since my last post I've aerated the pool, added 6 boxes of Borax, a little more than two gallons muriatic acid. Checked everything then added 24 cups of 6% Clorox because the cl was at 0, and added 2 3" tabs to a floating feeder. Here are the final results of the evening:

9 May, 23:32

Temp: 25.7

ORP: 714

pH: 7.59

fc: 13.5 (need to challenge as I think I still had a bit of static effect)

cc: 0.5 - 1.0. (wasn't entirely clear on first drop)

ta: 110 (measured with old kit, new still had serious static problem)

Optical clarity - still at around 95% but this is subjective.

Thanks again for all the help!

Mark

p.s. I did a single blind test of borates in the water by borating one 5 gallon bucket and filling another with un-borated pool water. I then asked my wife which one she prefered (because she had been complaining about how "dry" the water felt) and she immediately said the borated water felt smoother and less dry. I couldn't tell much difference but that's not really important :-)

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Give Dave a call or E-mail at tftestkits.net since he can send you new dropper tips if you can't seem to get rid of the static on the one you have. He should also be made aware of the static in the kit as a whole. He's very careful about quality control and would like the feedback.

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This would explain why my CYA drastically declined last year when I had the ammonia problem. My CYA was still too high, and I continued to do a lot of partial drainings and re-fills. I think I'm in the right ballpark now.

It's not biomass, but soil bacteria that can get into a pool that has no chlorine in it (usually over the winter if a pool is "let go") and can convert the CYA to ammonia. However, this doesn't always happen, is not controllable, and requires a LOT of chlorine to get rid of the ammonia and other intermediate products. Basically, the only practical way to lower CYA is by dilution of the water via partial drain/refill (or continuous drain/refill, but that uses more water).

Given your numbers for CYA, it is possible that bacteria did convert some of it to ammonia. It can happen in just a few days as happened to me this year when I stupidly didn't add chlorine mid-week as the pool warmed up (see this thread). However, since you are measuring FC, you've added enough chlorine to get rid of it (IF it converted at all).

As for the DPD chlorine test, it can bleach out above 10 ppm FC so you can certainly see the effect you saw where diluting the water results in a higher FC reading because the test isn't getting bleached out as much. This is one reason why the FAS-DPD test is better since it does not bleach out -- if you see a flash of pink when adding powder, just add more powder until you get the pink/red -- then add titrating reagent and count the drops (which are 0.2 or 0.5 ppm each, depending on sample size).

Since you are actually measuring a Free Chlorine (FC) level, you do not have any ammonia in your pool. Ammonia will not exist more than a few seconds to a minute or two in the presence of chlorine as it combines to form monochloramine very quickly. In your case, you are measuring some Combined Chlorine (CC), most likely due to the algae. Just shock the pool by keeping the FC at roughly 40% of the CYA level until 1) you measure <= 1 ppm FC drop overnight, 2) you measure <= 0.5 ppm CC and 3) the pool is crystal clear. See Defeating Algae for more details. The pool should clear and the CC drop within a few days since it doesn't sound like your algae bloom got very far -- for a big bloom it can take up to a week to clear the pool.

Richard

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(Comcast was down for a day or so here so I'm just not getting back on line)

I sent Dave an email and it hasn't been returned so I'm hoping I got the correct address.

I've kept a floating tablet feeder in the water hoping to raise the CYA. I haven't tested for it too much because I know it goes slowly and I also don't want it raised too much till I have the cc at zero.

We have not used the pool and not removed the solar cover since starting this, and we have kept the fire burning for the past two days. Yesterday afternoon the weather cooled by several degrees within a few hours and has remained cool since then.

There is also still some rain water on the pool cover from about two days ago.

Between the two evening tests on the 11th I added 182 oz (one large jug) of bleach because there was suddenly a high cc reading and low cl.

Questions:

Why did cc suddenly spike after being so low for so long?

How long am I going to have to keep the cl levels up to get rid of the cc?

Does it help to go to double the shock level or is it enough to just pass the breakpoint?

Maybe a constant but low level of cc indicates that something is being oxidized or "burned off"?

Most recent values:

Date : 5/9 5/10 5/10 5/11 5/11 5/11 5/12

Time : 23:32 ─ 11:12 ─ 19:47 09:27 20:27 21:39 10:23

Tmp°C : 25.7 ── 25.4 ── 26.5 ─ 24.9 ─ 28.0 ─ 28.2 ─ 27.0

ORP : 714 ─── 644 ─── 638 ── 645 ── 617 ── 649 ── 645

pH : 7.59 ─ 7.43 ── 7.32 ─ 7.27 ─ 7.17 ─ 7.39 ─ 7.30

FC : 13.5 8.5 5.5 5.5 3.0 13.5 9.0

CC : 1.0 0.5 0.5 0.5 1.5 0.5 2.0

TA : 110

CYA : 20

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If you don't hear from Dave, let me know. His E-mail (on the website) is tftestkits@hughes.net

Alternatively, you can post at Trouble Free Pool or PM him (duraleigh is his user name).

I don't know why the CC spiked unless something got into the pool or the test measurement was in error for some reason. At any rate, the rate of chlorine drop is high given the cover which should be protecting the water from the UV rays of sunlight (is the cover clear or opaque?). Perhaps the cover is clear enough to let UV through so the low CYA level isn't protecting the chlorine much from sunlight -- that might explain the FC drop though doesn't explain the CC.

After you've got the CYA up a little and continue opening up your pool, if you still find any issues including an overnight FC drop (which it appears you have from the last two readings, though the sun may hit the pool in the morning), then shock with an FC that is 40% of the CYA level and keep it there until 1) you measure <= 0.5 ppm CC, 2) you measure <= 1.0 ppm drop in FC overnight and 3) the water is crystal clear.

Richard

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Sheesh - if it aint one thing it's another.

Tacked the most recent three measurements on to last table and pasted below.

The cover is a standard Leslie's Pool Store blue/clear: there is a layer of bubble wrap on one side and a layer of blue plastic on the other side. It filters out all most visible light except blue, and I imagine it stops UV also.

I'm fairly comfortable with the test kit and the readings, I may not have rinsed the test beakers before the tests once or twice (always did it afterward so they were rinsed) but the most recent measurements are ok.

Over the day yesterday cl went from 9.0 to 8.5. I would have been ok with that but I still had a high cc level.

This mornings measurement was at 5 cl, thats a 3.5 ppm loss over night so I hit it with another shock. I didn't want to get the CYA levels too high yet. We've been having some cold cloudy weather recently so wasn't necessary to protect from sunlight, and I didn't want to have to use too much bleach to reach shock levels.

So after this mornings measurement I hit it again with 186 oz K-Mart bleach (cl concentration isn't labeled but it was on sale so I assume it is 5%). That raised the cl level to 14.5 - but it also got rid of the cc! Yea!

But every medicine has it's side effects and this one was ugly. Before I shocked this morning I saw that the beige stains are back.

To quote a certain cartoon character from Arlen TX, "Got dang it!"

I decided a grapefruit was appropriate for a mid morning snack so once I finished most of it I squished the remnants onto the stairs where the stain is visible but water is shallow and sure enough, nice round white spot where the stain was. So this means another round of waiting for a very high fc level to come down to near zero, a bunch of ascorbic acid dropped in the water, waiting around for the stains to go, then slowly raising the cl level again, hopefully this time with no cc.

I also had erratic readings from my ORP/pH meter again this morning. pH was saying 7.02 so I checked it with the drop test kit and it came up to what I expected - the bleach raised it somewhat.

- Could the cc be related somehow to the last citric acid treatment or the Metal Free by Natural Chemistry I used as a sequestrant?

- I have had a floating erosion feeder with two pucks floating in the pool since the CYA dropped out. I removed it today (the two pucks are almost gone) but could it be causing the stains/cc?

- Is there really any way to remove metals from the water or should I replace the water?

- Last testing at the pool store said no metals and tds was within reason. Should they be reading metals if I'm getting stains like this?

Date ── : 5/9 ─── 5/10 ── 5/10 ── 5/11 ── 5/11 ── 5/11 ── 5/12 ── 5/12 ── 5/13 ── 5/13

Time ── : 23:32 ─ 11:12 ─ 19:47 ─ 09:27 ─ 20:27 ─ 21:39 ─ 10:23 ─ 18:17 ─ 10:51 ─ 12:42

Tmp°C ─ : 25.7 ── 25.4 ── 26.5 ── 24.9 ── 28.0 ── 28.2 ── 27.0 ── 28.1 ── 28.0 ── 27.9

ORP ─── : 714 ─── 644 ─── 638 ─── 645 ─── 617 ─── 649 ─── 645 ─── 642 ─── 638 ─── 717

pH ──── : 7.59 ── 7.43 ── 7.32 ── 7.27 ── 7.17 ── 7.39 ── 7.30 ── 7.18 ── 7.13 ── 7.4

FC ──── : 13.5 ── 8.5 ─── 5.5 ─── 5.5 ──── 3.0 ─── 13.5 ── 9.0 ─── 8.5 ─── 5.0 ─── 14.5

CC ──── : 1.0 ─── 0.5 ──── 0.5 ─── 0.5 ─── 1.5 ─── 0.5 ─── 2.0 ─── 1.5 ─── 2.0 ─── 0

TA ──── : ─── ─── 110 ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ───

CYA ─── : ─── ─── ─── ─── ─── ─── 20 ─ ── ─── ─── ─── ─── ─── ─── ─── ─── ─── ─── ───

.

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Uh oh. Does that mean the drop test I used for the pH on the last reading (fc=14) was "bleached" and was giving me a wrong number?

After adding the bleach to the water I expected the pH to have risen about as much as the drop test showed. My electronic meter showed a much lower pH (< 7) and was fluctuating which I've come to learn means it is not reliable.

A later test (haven't posted yet) showed both again agreeing. I'll watch this.

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The pool store should have measured some metals if you ended up with staining. Fortunately, new fresh stains can often be removed by lowering the pH (that means having the chlorine level drop since the pH should drop some from that and then you can lower it a bit more if needed) and from adding a metal sequestrant. The ascorbic acid treatment is more for stains that have been around a little bit longer, though it does work on new stains as well.

The CC is odd. It's especially strange that it creeped up so quickly. Next time, you can try uncovering your pool since sunlight plus chlorine does tend to help get rid of them better. Metal sequestrant slowly breaks down from chlorine so perhaps when that happens it registers as CC at first and then when more of it broke down it released the metal and you got staining. So if that is what happens, it's probably better to ignore the CC, especially if there's no smell of it.

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Help me Obiwan-ChemGeek-Kenobi .... I feel like one of those Russian doll sets, only this time each doll you open is bigger than the one before, and there is no "biggest".

I think I understand now what is happening, so what do I do to interrupt it - short of drain and refill?

I agree with the estimation that the sequestrate is causing the cc. Just after I noticed the stains yesterday (at 10:51) and tested, I also added a little more than what the package of Metal Free by Natural Chemistry recommended should be a standard dose. While it didn't remove the stains as of a few minutes ago, it did remove the fc and gave me cc.

My best guess is that with the sequestrate in the water, the pool store will measure no metals because the sequestrate holds them back wish I'd kept a sample of 0 cc water to have the pool test but hindsight is 20/20). At the same time, the chlorine is "consuming" the sequestrate and that's why I get cc. (cc returned just after I added the large dose of sequestrate, and fc is way down overnight.)

So what it looks like I'll need to do is wait for a near zero fc level, do the ascorbic acid treatment/sequestrate once more, raise fc to appropriate sanitize for my cya, and then ignore the 0.5 cc that I will get from then on and assume a higher cl demand, keeping a weekly cap-full of sequestrate in the water.

I have removed the cover, we may have some sunshine today (dang, wanted to kep the temp up) and it looks like I won't have to wait long for a low fc level. For example now already.

My best test device for perceived water quality and smell has been my wife. While I can't calibrate her, the resolution is good and the sensitivity is fantastic. If I smell a slight chlorine odor, she says it stinks really badly. If I see a slight discoloration somewhere, she wonders where all those ugly stains come from. And when she starts seeing/smelling/feeling that something is wrong, I'm still looking at a perfect pool.

Her nose has been telling me that the pool has a strong odor, I only notice a slight intermittent smell. The visual water quality is ok though.

Is there anything else I need to think about?

Is there any way to get the metals out of the water, not just off the walls?

Once again Richard, thanks for your valuable input - especially at 3 am (I was there then too :-)!

Date ── : 5/9 ─── 5/10 ── 5/10 ── 5/11 ── 5/11 ── 5/11 ── 5/12 ── 5/12 ── 5/13 ── 5/13 ── 5/13 ── 5/14

Time ── : 23:32 ─ 11:12 ─ 19:47 ─ 09:27 ─ 20:27 ─ 21:39 ─ 10:23 ─ 18:17 ─ 10:51 ─ 12:42 ─ 22:56 ─ 09:09

Tmp°C ─ : 25.7 ── 25.4 ── 26.5 ── 24.9 ── 28.0 ── 28.2 ── 27.0 ── 28.1 ── 28.0 ── 27.9 ── 25.7 ── 24.5

ORP ─── : 714 ─── 644 ─── 638 ─── 645 ─── 617 ─── 649 ─── 645 ─── 642 ─── 638 ─── 717 ─── 642 ── 612

pH ──── : 7.59 ── 7.43 ── 7.32 ── 7.27 ── 7.17 ── 7.39 ── 7.30 ── 7.18 ── 7.13 ── 7.4 ─── 7.2 ─── 7.26

FC ──── : 13.5 ── 8.5 ─── 5.5 ─── 5.5 ─── 3.0 ─── 13.5 ── 9.0 ─── 8.5 ─── 5.0 ─── 14.5 ── 13.0 ── 2.5

CC ──── : 1.0 ─── 0.5 ─── 0.5 ─── 0.5 ─── 1.5 ─── 0.5 ─── 2.0 ─── 1.5 ─── 2.0 ─── 0 ───── 1.0 ─── 2.0

TA ──── : ─────── 110 ── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ───────

CYA ─── : ─────── ─────── ─────── 2 0 ─── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ───────

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So what it looks like I'll need to do is wait for a near zero fc level, do the ascorbic acid treatment/sequestrate once more, raise fc to appropriate sanitize for my cya, and then ignore the 0.5 cc that I will get from then on and assume a higher cl demand, keeping a weekly cap-full of sequestrate in the water.

I have removed the cover, we may have some sunshine today (dang, wanted to kep the temp up) and it looks like I won't have to wait long for a low fc level. For example now already.

Is there anything else I need to think about?

Is there any way to get the metals out of the water, not just off the walls?

This sounds like a decent plan though hopefully the extra sunlight and air exposure will help. You usually shock a pool with it uncovered to let the volatile disinfection byproducts outgas.

Your CYA is quite low at 20 ppm. If you raise it higher to 30 or 40 ppm, then that will protect the chlorine from sunlight better. so the swings in your FC should be less. You just increase your minimum FC level proportionately (see the Pool School and the Chlorine/CYA Chart).

Part of the reason there is more smell in your pool is that you have very high FC levels with low CYA. That combination makes the active chlorine concentration higher which creates more noxious disinfection by-products (nitrogen trichloride specifically). For normal swimming, your FC level should be in the range of 7.5% to 15% of the CYA level. Your wife will likely not notice much of a smell at that level -- my wife is sensitive as well and when the chlorine gets to around 7.5% of the CYA level she doesn't notice it and it's still very faint at 15%. Again, raise your CYA level some so that you can have better chlorine protection and a lower active chlorine concentration.

Richard

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Ok, went to the pool store (so why do they always smile when they see me even though I use BBB?) and left with over $100 worth of:

- ascorbic acid (I know, it's cheaper online but they can't deliver in 10 minutes, and it's not much cheaper)

- Metal Free (sequestrate)

- one gallon of liquid stabilizer (direction say I need 1 gal for a 34 ppm rise in 10000 gals so I'll probably use about a quart)

- one container of R-0013 (test reagent for cya)

I ran a complete test of everything (calc was 60 ppm) (last entry below) and then added the ascorbic acid.

Once again, within just a few minutes much of the stain was gone, but I am going to wait a while before I backwash and start adding cl. There's still a lot of general discoloration.

Amazing how much cl was swallowed overnight just by adding the sequestrate. I can imagine I am going have to fight again for a few days to get the fc back up.

Also I can't trust the electronic measurements. the temp can't be 27, the pH showed a little low so I used the drop kit.

The cya is now over 40 I believe because of the two tabs I let erode in the floating feeder. I'll probably add a little more - but not much.

Date ── : 5/9 ─── 5/10 ── 5/10 ── 5/11 ── 5/11 ── 5/11 ── 5/12 ── 5/12 ── 5/13 ── 5/13 ── 5/13 ── 5/14 ── 5/14

Time ── : 23:32 ─ 11:12 ─ 19:47 ─ 09:27 ─ 20:27 ─ 21:39 ─ 10:23 ─ 18:17 ─ 10:51 ─ 12:42 ─ 22:56 ─ 09:09 ─ 16:36

Tmp°C ─ : 25.7 ── 25.4 ── 26.5 ── 24.9 ── 28.0 ── 28.2 ── 27.0 ── 28.1 ── 28.0 ── 27.9 ── 25.7 ── 24.5 ── 27.?

ORP ─── : 714 ─── 644 ─── 638 ─── 645 ─── 617 ─── 649 ─── 645 ─── 642 ─── 638 ─── 717 ─── 642 ─── 612 ─── 340

pH ──── : 7.59 ── 7.43 ── 7.32 ── 7.27 ── 7.17 ── 7.39 ── 7.30 ── 7.18 ── 7.13 ── 7.4 ─── 7.2 ─── 7.26 ── 7.2

FC ──── : 13.5 ── 8.5 ─── 5.5 ─── 5.5 ─── 3.0 ─── 13.5 ── 9.0 ─── 8.5 ─── 5.0 ─── 14.5 ── 13.0 ── 2.5 ─── 0.0

CC ──── : 1.0 ─── 0.5 ─── 0.5 ─── 0.5 ─── 1.5 ─── 0.5 ─── 2.0 ─── 1.5 ─── 2.0 ─── 0 ───── 1.0 ─── 2.0 ─── 0.5

TA ──── : ─────── 110 ─── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ─────── 100

CYA ─── : ─────── ─────── ─────── 20 ── ─────── ─────── ─────── ─────── ─────── ─────── ─────── ─────── 40

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Pool is now again shiny and clean and new. I even made a video of the whole process and as I scatter the ascorbic acid around the pool you can see it start to act on the initial spot before I even finish moving all the way around the pool.

I let it do it's thing for several hours then added 2 quarts of bleach.

About 2 hours later I did a quick test of the cl and it was zero so I once again added 2 quarts.

Another 2 hours later it looks like about 2 ppm and ORP in the mid 500s so maybe the cl is holding for now - meaning the ascorbic acid is consumed and from now on I'll only have the Metal Free consuming the cl.

From those values I also think the cya may be lower than first thought so I'll recheck it again on Saturday (busy on Friday) though the low pH may explain why the orp was so high for that cl/cya combination.

The pH is of course low - around 6.8 - and I'm hoping it wont bother the heater core. It is stainless steel and I have other stainless steel parts around the pool that were not corroded by the previous owners ignorance of pH levels so I see no reason to worry but if anyone has another opinion I'd be happy to hear it.

Before swimming I intend to raise the pH. I was expecting to need more bleach and thought I might get away with raising it that way but it looks like I'll have to get my shop vac out again and run it backwards. This works great but is irritating. I could add baking powder but I don't want to get my TA up too high.

I confirmed the temperature really was at 27° which means the air is warming the pool. I don't get much direct sun but it was still surprising to see it go from 24.5° - 27.0°C in around 7 hours. It was a nice warm day here to so maybe not 27 but probably approaching that. I wonder if the chemical reactions going on in the pool might be exothermic?

Since I didn't really test well I wont bother with values but we can say there is a bit of cl in the pool, the ORP is at a bearable level for the night, and we'll see how it is tomorrow.

Wow, I just imagined actually swimming in this thing someday - d'ya think? .... Naaaww, Can't be!

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I am now in maintenance mode again with the fire burning in the heater but with a very high rate of chlorine use. So far it seems I'm using 8-16 cups of 6.15% bleach a day.

I think the summary is:

- CYA CAN dissipate from a pool very quickly, we just don't know yet which organism or mechanism is behind it.

- Metal (Iron at least) stains can be removed from the walls and floors very easily and fairly quickly with ascorbic acid and a sequestrate but the sequestrate will consume chlorine, and the sequestrate must be held at a minimum level. The sequestrate will also cause a small combined chlorine level that should be ignored.

- With a sequestrate in the water, go easy on the shocking.

... and last but not least ...

- Don't let the pool get below sanitize chlorine levels for any length of time! Even if the pump breaks down, add some bleach and slosh it around.

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Mark,

Yes, an ounce of prevention is worth a pound of cure.

I believe you posted elsewhere that your pool is 8500 gallons. So 8-16 cups of bleach in that volume is 3.6 - 7.3 ppm Free Chlorine (FC) per day. That is certainly higher than normal. You should compare your overnight (no sunlight) FC drop compared to the FC drop in the same period of time (number of hours) during the day. If there isn't much drop at night but there is a lot during the day, then the CYA level should be raised, along with the target FC. I don't think that's your situation given the numbers you've posted, but you can check to be sure (and things might change over time).

If you had 50 ppm CYA, then you wouldn't want the FC to drop below 3.8 ppm and if your pool was in a normal situation you'd likely go from 6 ppm FC to 4 ppm FC each day with almost all of this drop being in the day and minimal at night. That would be a 2 ppm FC per day usage which would be more typical. I'm just giving you an idea of what "normal" would look like (someday).

In your situation long term, water replacement will be the best way of getting rid of the metal that came from the rusted heater from the continued use of Trichlor without monitoring pH -- all from the previous owner of your pool. At that point, you won't need any, or certainly not very much, metal sequestrant so should have a more normal chlorine demand.

Richard

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Yep, I posted the 8,500 gal thing in my signature.

I checked overnight and it is dropping and I do have my basic 0.5 cc (no other specific numbers yet, a t-storm rolled through just when I started testing) though I'm getting the impression that the drop is slowing a bit. Right now I'm pretty convinced that the sequestrate is using the cl. Please tell me if this isn't the case.

I've restarted the fire and it's been burning since last night which makes me ponder how much the temperature effects the chemistry.

Also, the pH is still low - (I'm getting phone numbers or something else from my pH meter because it sure isn't pH - maybe need to calibrate) but I've discovered that on low speed I can slightly open a sample port on the return side and it will actually suck air into the return lines. So now I'm aerating slowly as well as using bleach to get the pH up.

I'm also going to set up an "IV drip for the pool" using a 5 gal camping water bag, some tubing and a valve to allow diluted bleach to drip into the pool. Not very pretty but effective.

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Right now I'm pretty convinced that the sequestrate is using the cl. Please tell me if this isn't the case.

The truth is I don't know the source of your chlorine demand, but the metal sequestrant is one possible source. If the rate of chlorine usage is dropping over time, then there might be something else in the pool slowly getting oxidized away. Though you'd normally shock to make that go faster, you can't do that in your pool due to the high metal content (sequestered or otherwise).

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I checked, sequestrant is the noun sequestrate is the verb. My stupid spell check didn't accept sequestrant ... but I digress.

It was pretty clear that the cc went away as soon as stain returned - or vice versa, and therefore my assumption that the sequestrant is the cause of the chlorine demand. The other part of this is of course the temperature. I still have the heat going but it has reached 30°C/86F° and I will be letting the fire die out over the next few hours.

We did have a nice swim this evening despite cloudy skies and coolish temperatures.

Not wanting to let cl go too low, and not wanting to get to shock levels, I've rigged up my bleach drip feeder.

I mixed one 192 oz bottle of cheap K-Mart (not strength marked but probably 5% when it was manufactured), with just a little more than two bottles full of pool water and put it in a 5 gal camping water bag.

I attached a 1/4" hose to the output of the bag and hung the bag in the pool tool box - cool and shady - and put the other end across the pool deck and hanging into the water.

I put an adjustable crimper near the pool end of the tubing and crimped it down to about 1 drop per second.

If my careful guestimated calculated values are correct (I counted 680 drops for two ounces then calculated up and back from there), that should slowly raise the cl level over time or possibly break even. I am guessing the bag last two or three days at this drip rate, barring failures on the water bag connection and any differences in the drip rate once the bag gets towards empty.

My last test showed about 2ppm cl, and just barely 1 ppm cc, and the ORP was in the upper 500s. As clear and clean as the water appears I can't Imagine there are any other contaminants but I will keep observing.

So my only question for today; Is there chemically any way to actually remove the metals from the water? I have read that Metal Magic by Proteam Products or one fo the Jacks Stuff will actually remove the metals. Is this accurate? (Ok, two questions.)

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So my only question for today; Is there chemically any way to actually remove the metals from the water? I have read that Metal Magic by Proteam Products or one fo the Jacks Stuff will actually remove the metals. Is this accurate? (Ok, two questions.)

Those products are metal sequestrants. They do not remove the metals from the water -- they just chemically bind to them so that they won't react. If they did this permanently and didn't break down with chlorine then for practical purposes they would be eliminating the metals, but unfortunately they do slowly react with chlorine. The MSDS for ProTeam Metal Magic is here while the Jack's Magic the Pink Stuff metal solution is here. Both are metal sequestrants (phosphonic acids).

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Phosphonic Acids? I guess I'm hooked on phosphonics then. ;)

I posted the details in another forum but I have managed to set up a chlorine feeder that is keeping the cl and ORP an appropriate level.

I sure appreciate the help Richard and I gotta tell you, despite the cost and complexity of this (at a chemistry level), I've learned a lot.

Thanks again!

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