Comments for Stable High Free Chlorine But Still Green Water

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Jul 14, 2011
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Update (Continued)
by: Anonymous

Last evening, the water was still very cloudy and still has a green tint to it. The FC is 22.5 and CC is very low (slight pink tint, one drop easily clears it ? I?m testing at the 10ml level since FC is so high).

This morning, the water is a little bit clearer (I think) but I have something settled out on the bottom, and it still appears green to me. The FC is still at 17 and CC is still low (<.5).

Why would I still have what appears to be growing algae when my FC is high and CC is practically 0? This is the same problem I always have. I get FC way up but it doesn?t seem to kill the algae. It made sense that it was high CYA locking up the FC. But now I have a test kit that shows the CYA is not unreasonably high. And now I can test CC and find that the FC doesn?t seem to actually be doing anything. Why? I could understand if I wasn?t shocking at a high enough level that I wouldn?t be keeping up with the algae growth but wouldn?t my CC be high in that case? Does chlorine simply not have any effect at all on certain algae until it gets up to a certain concentration?

In your original response, you said that CYA might be low. If the CYA was low, wouldn?t I have seen the FC rapidly dropping? In my case, the FC was high and stayed high. I?d suspect high CYA, not low.

I know everyone says to be patient but how do you know when to keep adding chlorine and when enough is enough? How long should it take to see all the green disappear?

Jul 14, 2011
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Update
by: PCDiem

Here?s an update. I suspected my CYA was high so I completely shut off the tri-chlor tablet feeder. I ordered a Taylor K-2006 test kit so I can have a better idea of what?s going in.

Funny story (sad actually): While I was waiting for the test kit to arrive, I went to the local pool store (The Great Escape) hoping they could test my water. I asked the two gals at the counter if the test water. One said ?sure?. I asked what it entails, how long does it take and how much does it cost. She said ?It?s east, I can do it right now and it?s free?. ?Sweet?, I thought and handed her my sample. She takes out a test strip (exactly like the ones I?ve been using) , dips it in the water and tells me that my chlorine is really high. I told them I knew it was really high but I still had green water. They told me that chlorine will not kill algae and I needed something to break it up. I figured I?d give they?re ?Algae Destroyed? a try. It?s 60% poly-quat.

I added the poly-quat and waited a day. There was no improvement. I wound up flocing the pool since we were having a party on the 4th. I hate flocing because it makes me feel like the pool defeated me. Of course, flocing didn?t solve the problem but it did get the water cleared up for the party. I figured since I vacuum to waste after flocing that it would also serve to reduce what I suspected was a high CYA.

My K-2006 has since arrived a few days later. By that time the water was getting cloudy again (not green but cloudy). My FC was down to 2.5, CC was .5, PH was 7.6, TA was 130, CH was 240 and CYA was 60.

I figured I should drain and refill to try to get the CYA down to around 50. As long as I was draining and refilling, I figured I?d floc again to clear up the water while I was at it. After vacuuming to waste the next morning, I added ½ gallon 12.5% sodium-hypo.

That evening, I had FC at 22, CC at .4, PH at 7.6, TA at 160, CH at 275 and CYA at 50. I added some muriatic acid to bring the TA down and added 1 lb. cal-hypo.

The next evening I had FC 2.8, CC .2, PH 7.8 (why did it go up?), TA 150, CH 225 and CYA 45. I added 1 gallon 12.5% sodium-hypo and 21 oz. muriatic acid.

The next evening I had FC 5, CC .2, PH 7.6, TA 140. I added some more muriatic acid to reduce the TA.

The next morning I had FC 4, CC .2, PH 7.5 TA 150 (why did it go up?). That evening the water was starting to get green and pretty cloudy. I added 4 gallons 12.% sodium-hypo and bushed all the walls. When I re-tested a few hours later, I had FC 22.5, CC very low (a very slight pink that one drop easily cleared) and CYA 50.

The next morning (yesterday) I vacuumed green algae from all over the bottom of the pool. I added another gallon of 12.5% sodium-hypo, added some muriatic acid (since I?ve read that chlorine works better at lower PH and I need to get my TA anyway), added some ?Algae Detroyer? (poly-quat) and put the solar cover on to keep the sun out.


Jul 14, 2011
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Comment
by: Robert

If you raise the CYA, the chlorine must be raised in relation to it. You can run the CYA at 100, but then the chlorine will need to be raised to around 7ppm to be effective.

You will still have algae because as you put the initial dose of chlorine in the pool, it will kill some, but not all of the algae. Yes, if you take a test a few hours later, you might get a 15 - 20ppm chlorine reading.

Many pool owners will say "Good, it's working" and they'll be right, but only to a point. The chlorine will come down quickly because the algae will consume the chlorine. When another reading is taken, the chlorine level will be low.

Another shock is needed, above 12ppm, and perhaps another, all the while maintaining a chlorine level of 12ppm or over for a long as it takes.

This is why it's so important to test morning and night and keep the chlorine level up.

The question says "Why would I still have what appears to be growing algae when my FC is high and CC is practically 0?" Your CC could be near zero, but there was a yo-yo going on with adding the chlorine.

One day 4 gallons was used, the next day only 1 gallon. Here's the inconsistency. Hit it hard, and keep hitting it. This part cannot be stressed enough.

Your chlorine level was high, at 22ppm, but not consistently. That's the part I wanted to stress when my original answer was "Keep manually dosing the pool in the evening, keeping the chlorine level at 12ppm, or over."

You would shock a 10,000 gallon pool with 1 gallon of chlorine, but your 15,000 gallons requires 1 2/3 gallons, probably 2 gallons, just to reach the 10ppm break point. This is why I always recommend going a bit higher on the chlorine dosing.

To reduce the alkalinity, the pump needs to be off and acid put in the deep end in one spot and gently sweep the area to break up any hot spots. Allow to sit for 3 - 4 hours, turn the pump back on, and allow for one full turnover of the water, then retest the alkalinity.

If your broadcast the acid around the perimeter of the pool, this will reduce the pH without much happening to the alkalinity.

Pool Alkalinity

Total Alkalinity

Your are correct in that chlorine is more active at a lower pH level. If you can get your pH level down to 7.2ppm that would be great, but don't stress about it.

Hope this clears up any confusion and let me know how it turns out for you.

Best of luck.

Robert

Jul 14, 2011
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Comment (contd.)
by: Robert

You did a good job in draining some of the water, but you need to lay off the floc for a while. Although it sounds like a good thing, it doesn't address the issue of why the pool is cloudy to begin with.

You should only be using liquid chlorine (sodium hypo.) for 2 reasons. First, the reason your pH went up after using cal. hypo. is because the pH in that kind of chlorine is 12. Cal. hypo. will always increase the pH level. 2nd, it has calcium as a binder. Your hardness level is 275ppm so you don't want to be adding any more hardness to the pool.

You need to keep the chlorine level up at 12ppm or over as often as you can. This is in my first response. The question said when the FC was at 2.8ppm, 1 gallon of 12.5% sodium-hypo was used. To shock a 15,000 gallon pool, you need to use at least 1 2/3 gallons.

Here are some pages and charts to look over:

Swimming Pool Chlorine

Pool Shock

Pool Chlorine

The next day 4 gallons of liquid was used, which is good, a little overkill, but better. That's when you got a FC reading of 22ppm. The chlorine started to kill more of the algae, but then the following day only 1 gallon of liquid was used.

This is the issue and a pattern can be seen. The chlorine get high, then low, under 12ppm), then high again. It must be kept high, morning and evening, above 12ppm as much as it can be, to kill the algae. This, along with back washing once per day.

It's basically this: Fry it and keep frying it with chlorine. Don't let up. 4 gallons is a bit much, but it's better than using 1 gallon.

In my first response it says "After you get the CYA in line, you can switch to liquid chlorine. I'm recommending this because cal. hypo. might increase the water hardness." It will do this and also increase the pH, which you don't want right now.

The first response also says "If the chlorine level has dropped by half or more, either you do have an algae problem or the CYA is off, either too high or too low."

The CYA needs to be at 30 - 50ppm for proper sanitizing of the pool. This is where chlorine is most effective at 1.5 - 3.5ppm (for weekly maintanence). At first the CYA level was at 30 with the test strips, but in acuality it was at 60 with the K-2006 kit.

Instead of being too low, it was a bit high for the chlorine you were running at the time.

CYA should be 7.5% of your chlorine level. CYA and chlorine are opposite sides of the same coin. If you run the chlorine at 2.5ppm, then the CYA should be 7.5% of that.

2.5 divided by 7.5% = 33.

Jul 14, 2011
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Comment
by: Robert

Thanks for the update & for the readings. It makes things go faster.

First off, test strips are ok, but a K-2006 kit will give you the best reading. There's only one of two reasons why the clerk at the pool store used test strips. She either doesn't know how to use the K-2006, or TF-100 kit (both are good) or she does know how to use it, she's just lazy. Sorry to be blunt, but it's true.

The question says "They told me that chlorine will not kill algae and I needed something to break it up" is absolutely 100% wrong. Chlorine kills algae. This is a problem I have with many pool store employees.

Ask the clerk how many green pools she has cleared up using an algaecide. Ask her how many acid washes, drains, refills, and water balances she's done when it's 116 degrees. Ask her how many complete filtration systems she's installed. Ask her if she can take an 80,000 gallon commercial pool and have it filled, heated, balanced out, and ready to go within 24 hours. You might be surprised by the answer.

You did use a PolyQuat 60 algaecide, which is good, but here's the thing about using it while you have an algae issue. Algaecides can't kill already existing algae. It's use for preventative maintenance only.

It's an insurance policy against another algae bloom while you're clearing this one up. If your chlorine level drops to zero, the algaecide is in the pool to help keep the algae away until you can shock again. Being that algaecides get used up, dissapate, and get back washed out, you need to keep dosing your pool.

Jul 14, 2011
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But Why High FC, Low CC & Still Algae Growth
by: PCDiem

Thanks for the additional input. As of this afternoon, the water is starting to get clearer and more grey than green. Hopefully I'm well on my way to conquring this outbreak.

I still have the question of why my FC was high yet my CC was so low and yet I still had visible algae growth. High FC, though maybe not high enough to keep up with the new growth, would still yield a high CC if it was killing algae, right?




Comment

By: Robert
Date: July 14, 2011

You did have a high FC level, although inconsistent. Hopefully that was remedied.

The CC level would show up, perhaps 0.2 - 0.4ppm, but it wouldn't be through the roof because you were in the process of killing the algae.

A low CC level, along with the white/gray color of the water, is what you want. They're both indications that the shock process is working.

The best thing is prescribed below. Keep the chlorine level up above 12ppm and keep filtering 24/7.

Hope this answers the question.

Robert

Jul 14, 2011
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What If FC Doesn't Drop?
by: PCDiem

What you recomend if CYA is around 50, PH of 7.5, very low CC, FC around 15 and dropping maybe 1 ppm/day and still see algae growth?

In other words, the FC of 15 doesn't really seem to be doing anything at all. Would you think I need a higher FC?




Answer

By: Robert
Date: July 14, 2011

Having a FC of 15 is fine. Keeping it there is the key. What happened is 1 gallon was put in, then 4, then 1. The chlorine level can't be allowed to get below the 10ppm point.

If you're only losing 1ppm of chlorine per day, that's a good sign that the chlorine is doing its job. When you put the chlorine in initially, it all went to the algae, which caused the level to drop.

If the pool is shocked again, but this time only 1/2 is lost, you're making progress.

Shocked again, and this time only 1ppm per day is lost, then you're winning. The chlorine has very little else to consume, which means the algae is dying or is dead.

Each time the FC was allowed to get below 10ppm, it's like starting all over again.

Algae grows very rapidly, that's why shocking each day, even hourly, can help precipitate the killing of the algae.

It will take several days to clear, but you should see progress each day if you keep the chlorine level up and keep filtering 24/7.

Robert

Jul 20, 2015
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Green Water
by: Anonymous

What is not stated here is that when algae forms on the pool bottom, it is protected by a bio film and unless you break that film, all the chlorine in the world won't kill it because it can't get through the bio film layer.

The solution is to rake all the walls AND the bottom with a brush attached to your pole. You will then see all this brown or green algae go into solution, mix with the pool water and actually turn the entire pool water to the color of the algae. This is good! This means you you have broken the algae bond that held it to the pool bottom and put it into solution which then allows the chlorine to reach it and kill it. The chlorine can then also attack the crevices in the pool surface and kill the areas where the algae was attached to the pool.

Once this is done, nuke it with 15-25 ppm FC and hold it there for several days. Scrub the sides and bottom again after the first and second day to break-up any residual algae attached to the pool bottom. Continue this until the pool is clear.

Jul 20, 2015
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Algae in Pool
by: Anonymous

10-25 ppm FC will kill almost anything in the pool provided the CYA levels are within norm and provided the chlorine can get access to the algae. Algae is protected by bio film and chlorine cant get through it very easily.

If you continue to see algae after high FC levels are used, it means your chlorine cannot get through the bio film surrounding the algae. To expose the algae you need to thoroughly brush the side walls and pool bottom to lift the algae and expose more algae surface area to chlorine. This will turn the pool into a swamp green or brown color, meaning you have lifted the algae from its attachment points. Do this daily for 2-4 days all while keeping the FC levels high (15-25 ppm) and you will kill it. If you don't, it will temporarily clear up and the algae will reappear as "dirt" on the pool sidewalls and bottom because you didn't kill the algae in the crevices where it attaches to the walls and bottom. "Mechanical scrubbing" lifts and exposes the algae so the chlorine can kill it.

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