Wrong Colors !?!

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
JPlunket
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Wrong Colors !?!

Postby JPlunket » Mon 06 Apr, 2009 20:19

Using a Taylor test kit, testing for total alkalinity, the recipe is two drops of 007, five drops of 008, which turns green; then 009 dropwise till red. For months, it has turned the normal red at about the 15th drop, so 150 TA. Oddly, the last few times, the green is distinctly bluish, and the color changes to a straw-color --the first time, I thought I was in a bad light, so I re-did the test with same results, then I waited several days, and again --008 turns the 007 NOT green but bluish, then about 15 drops of 009 turns it NOT red, but a light yellow. What's going on?

CYA is still off the chart --I don't get halfway to the 100, on the logarithmic scale, before the black dot disappears.

CH is still way high, 500ish.

Chlorine --changed from dichlor to 6% sodium hypochlorite, super-shocked with 1.5 gallons in 5000 gallon pool.

pH has remained fairly low, usually 7.2, but I've gotten to about 7.3.

This is a minor mystery, but I hope someone can teach me something on this.

I'm grateful to have learned last week that my high CYA was the cause of my algae problem --I was religiously maintaining the 1.5 to 2.0 Endless Pools recommends, with the copper filter cartridge, but the CYA made that low level completely ineffective against those nasty mustard algae, and it wasn't until I pushed the copper algaecide, did heavy shocking and kept chlorine in the 5-10 range that I beat them back.

Unfortunately, I worsened the CYA by doing all that shocking with dichlor. FOr two weeks, I've been using only 6% sodium hypochlorite and keeping it "redder than 10". No more eff'in' algae for me.

As soon as I take down the bubble and get a few dry days, I am going to take the water level down and refill with fresh, to try and get CYA, CH and TA back to where they should be.

Trying to be totally methodical, I need to know whether the false color reading are trying to tell me something.

Thanks in advance for any advice.


chem geek
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Wrong Colors !?!

Postby chem geek » Mon 06 Apr, 2009 20:51

As noted here , high chlorine (or bromine) levels can change the TA test so that it goes from blue to yellow instead of green to red. Your addition of 1.5 gallons of 6% chlorine (are you sure they are gallons? if they are bleach, these usually come in 3/4 gallon jugs or sometimes 1.5 gallon containers) in 5000 gallons increases the FC by around 18.5 ppm so would explain the TA colors you are seeing. The pH test won't be accurate in this case and can falsely read too high, though that does not appear to be happening in your case. Odds are that with that amount of chlorine, the pH is actually very high so not sure why you aren't seeing that.

As you mentioned, with CYA and CH very high, more dilution with water is needed.

I'm a little surprised that the copper wasn't enough to prevent the mustard/yellow algae, but clearly the chlorine was ineffective with the very high CYA level. Glad you finally got that sorted out. Yes, you are right that shocking with Dichlor was the wrong thing to do. One should NEVER shock or even use Dichlor unless they intentionally want to increase their CYA level (in addition to chlorine).

Sounds like you've got a good plan.

Richard
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Wrong Colors !?!

Postby JPlunket » Tue 07 Apr, 2009 14:42

I have always used dichlor, except for short periods when I ran out. As I recall, dichlor was recommended because it maintained CYA, which slowed the loss of chlorine from sun and sweat. I'm wondering: why is it recommended by many, sold everywhere, and specified as a shock treatment on the bucket as well as at the Pool School?

Having studied up some more at the Pool School, I am going to try liquid bleach, since I have high CYA and high CH.

I did put a full 1.5 gallons of 6% in, but I see that with my high CYA, the resulting 18.5ppm chlorine bump, combined with my 10ppm starting point, was not even really enough to have a shock effect.
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Wrong Colors !?!

Postby chem geek » Tue 07 Apr, 2009 17:19

Well, 28.5 ppm FC is pretty high, but you are right that if your CYA is 200 or more, then this isn't even a shock level of chlorine (an FC around 40% of the CYA level for normal algae killing; 60% of the CYA level to kill yellow/mustard algae quickly) though it does probably kill algae slowly at that level.

The following are basic chemical facts that are independent of concentration of product and size of pool.

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

When you add stabilized chlorine, it eventually gets used up either from breakdown from sunlight or by oxidizing organics. The Cyanuric Acid (CYA), however, does not break down so it builds up over time as noted above. It is only removed via dilution of the water. Evaporation does not remove it nor anything else except water, so chemicals just get more concentrated from evaporation and then fill water just adds its contents to the pool so the CYA level doesn't change from evaporation/refill (though CH and TA can climb if present in fill water). Splash-out and backwashing will remove CYA, but unless you backwash every week and have a small pool and a short swim season, then CYA will still climb. Rain overflow can also dilute the water and lower the CYA level. There is also the situation where letting a pool go and get to zero chlorine can sometimes have soil bacteria that get into the pool convert the CYA into ammonia.

If you even had a low chlorine demand of only 1 ppm FC per day, then using Trichlor, after 6 months you will have added 108 ppm CYA. If you used Dichlor, then you would have added 162 ppm CYA. It doesn't take long to build up the CYA. In my own pool 7 years ago, my CYA went from 30 ppm to 150 ppm in a year and a half (11 months of swim seasons with a winter in between) at a relatively low 0.7-0.8 ppm FC per day usage with Trichlor tablets/pucks in a floating feeder. I had a cartridge filter so had no backwashing and had no rain overflow (a pool cover pump drained water to a sewer). At some point, my chlorine usage went up and I could no longer keep up with it easily. My water started to turn dull which was a nascent algae bloom. And this was in spite of using an alagecide, though I was only using it every other week instead of every week. When the pool store was of no help, that's when I decided to learn pool water chemistry and find out the truth of what was going on in my pool and ran into The PoolForum / PoolSolutions (not accessible anymore from all IP addresses -- Trouble Free Pool is essentially its successor).

Some pool stores have poorly trained personnel while others are trained by the manufacturers' reps and their literature. Most of these manufacturers of chlorine products sell stabilized chlorine (Trichlor and Dichlor) so push those products and don't talk about how quickly CYA can build up or they'll say that higher CYA levels aren't a problem, sell Dichlor for shocking, etc. None talk about the FC/CYA relationship even though it's been known since at least 1974 (see the paper in this link ). Even today, they generally deny and obfuscate claiming that the scientific experiments done in labs don't apply to "real pools" or they say there have been no studies correlating CYA levels with disease outbreaks. Then again, the tobacco industry deceived consumers (and doctors) for 40 years; it's only been 35 years since 1974 so give the pool industry some time to come around. :silent:

When you said that Dichlor was "specified as a shock treatment on the bucket as well as at the Pool School", what do you mean by the Pool School? The Pool School I link to does say that Dichlor is sometimes sold as 'shock', but it also says this is not a good idea since it will raise CYA levels fairly quickly. Is that what you meant?

Richard
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Wrong Colors !?!

Postby JPlunket » Tue 07 Apr, 2009 20:54

Pool School: "Dichlor - Somewhat less common than the three forms above, dichlor contains both chlorine and CYA. Easily dissolvable, it is an excellent shock source of chlorine as long as your pool doesn't already contain too much CYA."

I wouldn't have properly understood that last qualification. Last year I got sold on the need for CYA, and chose dichlor as the best way to get my chlorine stabilized. Must have been the same pool store guy you know, since I never heard anything about CYA building up permanently.

It appears I can lower CH from 500 to 300, and CYA from 150 to 50 by replacing 67% of the water with my 250 CH tap water. Is CYA at 50 adequate to stabilize the bleach? Is there a particular testing regimen you recommend for determining the actual rate of chlorine dissipation? Or is there a rule of thumb on that, as a function of CYA concentration?
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Wrong Colors !?!

Postby chem geek » Wed 08 Apr, 2009 01:34

Thanks. I see that in this post at the Pool School that the Dichlor is mentioned as great for shocking. I'll write to dispute that. Only if your CYA level is very low should Dichlor be used for shocking. Note that item 2 says the following:

2. Pucks - (trichlor) Solid round discs that you simply put into an automatic container that passes pool water over them and they slowly dissolve - putting chlorine and CYA into your pool. They are incredibly convenient and incredibly insidious. The CYA that they put into your pool water never goes away and, in fact, continues to build. Building often to a point that it can render your chlorine ineffective. You start to develop algae and don't understand why.


The same is true with Dichlor in terms of the build-up of CYA, though that isn't clear.

Yes, 50 ppm CYA is usually enough to protect chlorine from breakdown from sunlight. In very intense sunlight with long days, sometimes up to 80 ppm CYA is better, but you have to maintain a higher FC level at the higher CYA level unless you use a supplemental algaecide or phosphate remover. As for the actual rate of chlorine loss, get yourself a good test kit with a FAS-DPD chlorine test. You can either get the Taylor K-2006 kit at a good online price here or the TF100 kit from tftestkits.com here with the latter kit having 36% more volume of reagents so is a little less expensive "per test". With the accurate FAS-DPD test, you can determine your rate of chlorine loss during the day (overnight the loss should be < 1 ppm FC).

There isn't a single rule-of-thumb, but roughly speaking at lower CYA levels such as 30-50 ppm one can lose 1/3rd to 1/2 of the chlorine in direct sunlight in one day during the peak of summer while at higher CYA levels such as 80 ppm one can lose about 1/4th the chlorine in the same situation. Even if the FC is proportionately higher at the higher CYA level, the absolute FC loss is sometimes less than at lower CYA levels.

Richard
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Wrong Colors !?!

Postby JPlunket » Wed 08 Apr, 2009 06:43

Thanks for the very useful information, professor!

Check my math?

at CYA 50, I'm aiming for chlorine 6. use that as where I start...
assume max sunlight, I'm losing 1/3 - 1/2 daily, or 2 - 3 ppm
5000gal X 128oz/gal divided by 1MM parts divided by 6% solution = 1 "part" = 10.7 oz
So, I would add 2 - 3 parts, or about 22 - 33 oz of 6% solution daily
indicating there are about 6 - 9 daily doses in 1.5 gallons of 6% bleach
to achieve "shock value", I need to add a daily dose plus 14ppm, or an extra 150 oz of 6%.

Do I have that correct?

I have the Taylor k2005, not available at SPS site, but looks the same as 2006, actually a couple more items in it, so I guess I'm good to go on that front.

Now my challenge is what to do with 3300 gals of nice clean water, and where to find the best deal on bleach, by the tanker truck load. Maybe Costco --any ideas?
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Wrong Colors !?!

Postby chem geek » Wed 08 Apr, 2009 11:11

You can use The Pool Calculator for calculating dosages. If you are using 6% unscented bleach (e.g. Clorox Regular or an off-brand Ultra), then 3 ppm FC in 5000 gallons is 31 fluid ounces -- basically 4 cups or 1 quart. That's probably the worst case per day usage -- it'll probably be less than that unless you swim in the pool a lot (i.e. higher bather load).

You will likely have to add the chlorine every day or possibly every other day unless you use a pool cover. With a clear plastic bubble-type pool cover, you can get good heating in the pool, eliminate evaporation, and possibly be able to add chlorine only twice a week. That's the situation in my own pool except my cover is an opaque electric safety cover. My daily chlorine usage is around 1 ppm and the pool is used every day (i.e. open) for about an hour or two.

If you properly maintain the chlorine level in your pool and never let the FC get below 3 ppm FC with 50 ppm CYA (better to target 3.8 ppm FC as a minimum to be safe) then you will likely never need to shock the pool. The chlorine is continually "shocking" the pool in terms of eliminating bather waste. Shocking is normally not necessary. I didn't have to shock my pool even once last year (except right after opening, just for the heck of it).

The Taylor K-2005 has the same items as the K-2006 except that the chlorine test is different. The FAS-DPD chlorine test is better than the DPD test you have. The FAS-DPD chlorine test is shown in a demo here where you can see how you just count the drops until the color turns from pink to clear. It's accurate to within 0.2 ppm FC with a 25 ml sample or 0.5 ppm with a 10 ml sample and can measure up to 50 ppm FC without bleaching out (the DPD bleaches out above around 10 ppm FC). You can get just the FAS-DPD chlorine test here .

Your pool store may sell chlorinating liquid which is basically stronger bleach, usually 12.5% or 10%, and it may be a reasonable price. Also, they may reuse (refill) the bottles so that saves on recycling. That's what I do where I buy 12.5% chlorinating liquid from my local pool store.

You point out the one downside to using the hypochlorite sources of chlorine. They need to be added daily or every other day unless you have a pool cover. Another downside for bleach or chlorinating liquid is that it is heavy to carry. You can get automated chlorine dosing systems including peristaltic pumps or The Liquidator or you can get a saltwater chlorine generator (SWG) system, but there are pros and cons with these systems as well.

If you want insurance in case your chlorine gets too low, then at extra cost you can use a weekly PolyQuat 60 algaecide (about $1 per week for your sized pool) or use a phosphate remover. Of course, if you use these, then Trichlor pucks wouldn't be as much of a problem, at least for a while.

Richard
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Wrong Colors !?!

Postby JPlunket » Sun 12 Apr, 2009 19:12

CG,

Using your math (as I understand it), I am just now coming to grips with the nightmare I created for myself by using dichlor without regard to its CYA effect.

I calculate I added at least 1,037ppm CYA ! I would be most obliged if you would take a moment and check my math.

the pool has been open 96 weeks / 672 days
I added about 1ppm each day, to maintain 2ppm FC
(I use Nature silver sticks in filter, but "to be safe" I stayed above the 0.4 guidance)
I shocked about every week (!), by adding at least 5ppm

dichlor added:
672 x 1ppm = 672 ppm from daily
96 x 5ppm = 480 ppm from weekly
total = 1,152 ppm
9 CYA / 10 dichlor = 1,037ppm CYA

This would seem to be confirmed (at least order of mag), since I drained about 3,000 gallons out of 5,000 gallon in the pool, and STILL my CYA black dot disappears before I get half way to the 100 ppm mark. Treated pool water, after this massive dilution, is still noticeably cloudy in the test vial.

Sheesh, no wonder I had the algae problem --the chlorine in my pool has basically been virtually inert from the 10th week onward. Also, no surprise it took a massive copper treatment to get rid of it --maybe it's a high residual level of copper that's been keeping the water algae free since?

I'd love to hear I'm off by a factor of ten or something, but I think this reflects the math you explained --can you confirm or correct?

Many thanks --this will have been enlightening, if also quite an embarrassment.
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Wrong Colors !?!

Postby chem geek » Sun 12 Apr, 2009 20:11

Don't be embarrassed. It's not your fault and is really the responsibility of the pool store for not telling you. Actually, the pool store was just relaying what they were told (or not told) by the manufacturers of stabilized chlorine products.

Anyway, your math is correct, except it does not account for normal dilution. There is some dilution from splash-out, but most dilution comes from cleaning filters. For example, if you have a sand filter that you backwash regularly, then the water is getting diluted. Also, if you have rains that fill the pool and spill-over (say, to a drain) then you have dilution. Finally, chlorine slowly oxidizes CYA so at very high CYA levels I'd expect some of the chlorine to oxidize it faster, though perhaps not more than around 10 ppm CYA per month (which would consume around 25 ppm FC per month).

If there was no dilution except for your partial drain and refill, then you would have around (3/5)*1037 = 622 ppm CYA. Your reading on the CYA test shows you have at least 200 ppm CYA, though is probably quite a bit higher than that. However, if your pool water is cloudy, then this can give you a falsely higher result, though not by that much. See if you can see the black dot when adding pool water to the top of the vial without adding any CYA reagent -- if you can still see the black dot, then your result isn't affected that much.

Yes, having copper in the pool will keep it algae free, though you have to be careful about staining, especially at higher pH.

Richard

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