Problems with algae and milky water HELP

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pv5490

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Mar 18, 2014
9
Florida
I am in charge of two different pools. One has 488600 (swimming pool) gallons of water and is heated, and the other one has 990750 (diving pool) gallons of water and is not heated. They are both old concrete pools. First I must clear out that the swimming pool has a new recirculation system working properly, while the swimming pool has an old recirculation system and the filters' sand need to be changed (Owner hasn't changed it in a long time, but will change the filters later on this year).

These pools usually receive about 600 people per day and exposed to heavy sunlight. "Fresh water" is taken from a pond (Analysis to this ponds will be made next month), but from what I tested with the Taylor kit, it has no chlorine and pH is below 7 (It was too yellow to give a reading).

With the swimming pool:
Pool guys used to alternate between trichlor and calcium hypochlorite (Both granulated). They didn't have a testing kit so I got one and got the following readings:
pH: 7
FAC: 7.5ppm
CAC: 0.5ppm
Alkalinity: 70ppm
Cyanuric acid: 85ppm
Calcium Hardness: 190ppm

In a week the pool turned completely green, so we closed the pool and when I tested pH, FAC, CAC it read as following:
pH: 7.2
FAC: 3
CAC: 0

I shocked the pool, first I had water replaced to lower the CYA and added 170lb of calcium hypochlorite. FAC went up to 16ppm instead of the 30ppm I was reaching for. I added another 170lb and it went up to 22ppm. Since the pool was not changing and people HAD to use the pool (No option there, I didn't have much time to reopen it) I decided to use 15lb of copper sulphate (I know it is not what TFP recommends, but I didn't have much time). Next day I vaccumed the pool and it was turbid, but not green anymore. I tested again and the readings were:
pH: 7.3
FAC: 13ppm
CAC: 0.5ppm
Alkalinity: 90ppm
CYA: 60ppm
CH: 200ppm

It is important to point out that the pool was being brushed twice a day.
So, according to the levels I found, everything was in order, except that chlorine was too high (Which made sense due to the amount of calcium hypochlorite used). I decided to mostly use calcium hypochlorite because I didn't want to get levels of cyanuric acid high again, but the pool started to get white and milkysh. Pool guy (He has a lot of practical experience) says it is because of the calcium in it, but I am not quite sure... They swear over trichlor, they even use it to shock the pools, with no regard over cyanuric acid buildup.

Now, with the diving pool:
They alternate trichlor and calcium hypochlorite every other day.
Their readings were:
pH: 7.3
FAC: 3.5ppm
CAC: 0ppm
Alkalinity: 110ppm
CYA: Over 100pppm
CH: 320ppm

Pool turned milkish and then turned green (Which is how it is today). Since we ran out of calcium hypochlorite (And can't buy any soon), I agreed to their suggestion of shocking with Trichlor (I know it's not right, but there is nothing else), so they added 75lb last night. With that FAC went to 4.5ppm (Which is nothing to what it should have changed). I thought they didn't add it, so I told them to add 110lb of it (Which they did, right in front of me) to the pool. I tested after a bit more than an hour (Taking into account trichlor takes a while to dissolve, but it only went up to 5.5ppm!! I know trichlor is supposed to go in skimmers, but either pool has skimmers, and they are both stained, so at this moment I'm not worried about the effects of trichlor in the pool's surface... I figured I'd kill whatever is in there with chlorine from trichlor, but at 5.5ppm it's not even close!

My main questions are:
-Is there a reason why 185lb of trichlor will only change FAC by 2ppm? I'm using Chinese products... The supervisor that was before me said that it is because chlorine goes directly into attacking algae and bacteria, but that doesn't make sense to me. From what I understand, high concentrations of chlorine will kill algae and bacteria, but chlorine does not act directly on algae without affecting concentration... Right?
-Why is calcium hypochlorite turning water white and then green if levels of chlorine are on the right level according to the CYA content, and alkalinity, pH and CH are fine as well (As they are in the swimming pool)?
-Pool guys swear that the white stuff in the pool is calcium, but calcium hardness is not too high. Does anyone have a better explanation on what this white powder-like stuff is? How do I fix it?
-Pool guys say that trichlor makes the white go away because it "traps all the white stuff and makes it go down". Does that make sense? According to what I know, trichlor is not a clarifier, it just adds chlorine and cyanuric acid to water.
-Any recommendations? I want to optimize the use of reagents and manage the levels smartly in those pools, but I can't do it if when I use less trichlor and more calcium hypochlorite (To avoid CYA buildup), water turns white.

HELP! Please. I'm confused....

Thank you in advance for everyone's help.
 
:wave: Welcome to TFP!!!

Admittedly I did not read the whole thing and jumped to the questions:
1. What kind of test kit are you using for the chlorine? If it is the pink DPD test that only goes up to 5ppm or so, it gets bleached out at high FC levels. So it could be very high, but the test shows low.

2. Cal-hypo adds a lot of calcium to the water, in the right conditions it can make the water white.

3. I am not sure what white stuff you are talking about since I did not read everything :D

4. Bunch of non-sense. The trichlor also lowers the pH in addition to adding FC and CYA.

5. Not sure. We generally help people manage their private pools. When there is a problem, we recommend following the SLAM Process and that just may not be feasible for these large public pools that can not be closed for potentially weeks.

From the bit I have scanned through your post, it seems like you have a generally better understanding of the chemistry than most of the other pool guys you have encountered :goodjob:

BTW, we never recommend adding any chemicals in the skimmer (except maybe CYA and then ONLY if the pump is run 24/7).
 
Your CYA level started at least a little too high and then you added trichlor, which contains both chlorine and CYA, which raised the CYA level further. As CYA level goes up, chlorine becomes less and less effective. Trichlor also tends to dissolve slowly, giving the algae more time to deal with it. Algae and chlorine do tend to react fairly quickly. With both the slow dissolving and the CYA level slowing that reaction down, it is unlikely that the FC level ever came up to shock level.

Now, with CYA really high, you have only a few choices, none of them especially good. Our normal recommendation is to replace perhaps 2/3rds of your water to get the CYA level down to something reasonable. If you can't do that, you are going to need a truly massive amount of chlorine, and this time something that dissolves instantly and does not contain either CYA or calcium (because either one will get completely out of hand given the amounts you will need to use). Bleach/liquid chlorine is the only plausible choice, as your other option, lithium hypochlorite, is going to be quite expensive.

The white stuff is almost certainly calcium, precipitated out and redissolved as the PH fluctuates in the immediate area of the chemical additions.
 
Hello! I know, it was too long :S

I'm using the Complete FAS DPD k2006 Taylor kit, the one that is based on titration instead of color. When I slammed the other pool it did read 22ppm.

Sorry about the skimmer comment, I must have read it somewhere and got the info mixed up. :).

Thank you, I have been reading a lot and really want to do a good job, but this becomes quite hard when pools begin to turn white and green. :'(
 
No matter which chlorine form you're using, it sounds like it's doing its job; that is, the moment it goes into the pool, it is being consumed in the algae killing process.

I'm with Jason. You need to get the FC level up to SLAM values and you need to do it fast. You're going to need bleach and a lot of it.
 
Thank you for your response,
I know :(, it started a bit too high with the CYA, but that was the best we could get considering it took us around five days to empty and fill out 5 inches of water in the pool (Which was about 1/5 of the pool)...

I tested again and:
pH 7.3
FAC 4.5
CAC 0
Alk 80
CYA 65-70
CH 190

I know chlorine levels were a bit too low for CYA, but I wonder why if CH is at 190ppm, and CYA levels are not over the top, the pool turns milky white if I use Calcium Hypochlorite and not Trichlor.
It just seems that both are a problem, because trying to maintain a CYA of 65ppm with chlorine of 7-8ppm (Which seems appropriate due to the amount of swimmers and sunlight) with only Calcium Hypochlorite turns the pool white, and using only trichlor elevates levels of CYA... I don't understand if that calcium hypochlorite is real bad quality and that could be affecting it, or is something else...

Thank you :).
 
Welcome to the forum pv5490. Those are enormous pools! :shock:

If you are going to use liquid forms of Chlorine, you will need very large bulk amounts of 12.5% on hand to do it. Especially doing a SLAM with a Cya reading that high. I don't know if it would be allowed, but those pools are good candidates for gas Chlorination as a FC source. To get them clear at least, you might seek local services that use Chlorine gas. Not many are left, but there are some. I normally would not suggest a pool service, but this is a really different situation. The addition of powders is going to further your problems as you have already seen.

We are focused on residential pool care and while the chemical principals we teach will not change in any size pool, the advice we offer will be limited in terms of practicality. Do stay, and enjoy the forums and continue to learn here, but please remember this is very different because of the sheer pool volumes you are dealing with.
 

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I may have a temporary solution to your issue. I would only suggest this to commercial pools that struggle with not being able to close down to the public for the 5-10 days of adequate SLAMing. I maintain two smaller commercial facilities and can never seem to get the closing time to truly SLAM the pool as this forum suggests. Here is what I do:

As you know your CYA level is probably too high to economically SLAM with high levels of CL. Plus being open to the public you must maintain state regulations. I've found that a Polyquat 60 treatment over two weeks or longer will slow down the algae growth to the point where a good bump in chlorine will begin to reverse the growth.

In my case, if I find my water looking dull and I suspect an algae bloom I remove ladders and clean light niches' then add Polyquat 60 (6 oz per 10,000 gallons) bumping my water up to a target of 5ppm each day. For the next few weeks I use a maintanance dose of Polyquat 60 ( 2 oz per 10,000) and start to bring CL down to normal levels (2-3 ppm is prefered by my local health department). Running vacume each night durning the entire process since algae will begin to fall to the floor.

After the first dose I see a lot of milky white within 24-36 hours. After that I see noticeable improvement each day. About two weeks in I feel like water is about as clear as I can get it with bather load factor.

Keep in mind that you truly need to lower CYA to economically SLAM (5-10 days) and then maintain a normal CL for daily maintenance; but if you don't have the time this may help.
 
Wow, tough situation. If he doesn't have access to chlorine gas or it's not permitted in his area, is his only real option to stock up on barrels and barrels of 12.5% bleach?? Would ozone/UV be of any use in these special circumstances?
 
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