Can you get algae if FC is within target?

[OneMom]

Hi All:

We must be misunderstanding how this all works, because I didn't think we could get algae if our FC stays within the target range indicated by our CYA level.

This is the scoop. Our CYA has been between 50 & 55 this past month. Our CC level has stayed at 0. Our FC has been high since we raised it to 27 back on Aug 13 when we started an algae bloom. We kept the chlorine at that level until we didn't lose chlorine overnight. Just to be safe, we then kept it at 27ppm for another 48 hours. Since that time, we haven't added any more chlorine because we were letting FC drop to normal levels. We didn't notice any more algae until 8/20.

On that date, our FC tested at 22. Our water was clear, but the bottom had a green powdery substance that dissolved when it was touched, no scrubbing was needed. There weren't any spots on the sides of the pool. The vinyl & steps weren't slimy - they just had that green powdery residue. Since the FC was still so high we assumed that what we were seeing in the pool is the pollen that everyone on this forum has been talking about.

We continued to vaccum & backwash as usual, but each day we'd still see that stuff on the bottom of the pool. We didn't add any more chlorine, the FC still hadn't dropped into normal range yet.

By 8/31, our FC was at 12. It held at 12 (we had the solar cover on) until 9/5 (two days ago). We still were seeing the green stuff, but the water was clear & CC was still 0. Yesterday (9/6) the water was cloudy & the pool was covered with a full bloom of green algae. There isn't any on the walls, it's not yellow, but it's definitely slimy. The FC level had fallen to 6. We are now adding chlorine to shock levels. We keep it at that level for 24-48 hours PAST when it has held overnight without the FC level dropping.

So...what are we doing wrong? Why do we get algae even when our FC is within the target range indicated by Chemgeek's chart? Our solar cover has been on a lot. Will that cause it? This is the first year we used the BBB method & haven't used algaecide. Now we're wondering if we should start using it again.

By the way, our Ph is at 7.3 and our TA is at 110. Both PH & TA have stayed within normal limits this past month.

 

[duraleigh]

Well, the conditions you describe are certainly not conducive to algae. My next thought would be a testing error but it sounds like your testing with an FAS/DPD chlorine kit, is that correct?

 

[OneMom]

We have a Taylor FAS-DPD kit. (The label says it's a K-2006) We got it from Leslie's Pool supplies.

 

[dawndenise]

How often have you been running your pool's pump/filter? What has been your normal schedule?

 

[JasonLion]

I wonder if your CYA test is really right. I have trouble imagining FC levels staying reasonable for three weeks with CYA of only 55, even allowing for the solar cover. Also at lower FC levels the FC level goes to zero very quickly when you have algae, while you still had a reading of 6 after a "full bloom of green algae". And finally at CYA of 55 a FC of 6 or 7 should have been enough to keep algae away, but higher CYA would have allowed algae. All of those are suggestive of much higher CYA levels.

 

[ric]

Hi OneMom
Is it at all possible you would be getting the decimal point in the wrong place when you do the CL test this has happened to people before. Are your regants up to date? and dawndenise has a good tip on the pump.

 

[chem geek]

A green powdery residue that settles to the bottom, dissolves when touched, and is not slimy does not sound like algae to me. It sounds more like some sort of precipitate, possible copper carbonate. That would be a bit unusual at the low pH and TA levels, but the pH test won't be accurate at high chlorine levels anyway (though usually it reports too high a pH, not too low). I estimate that a copper level above 3.6 ppm could precipitate as copper carbonate at a pH of 7.3, TA of 110, CYA of 50-55.

So I would have your water checked for metals to see if that is the problem. If it is, then a metal sequestrant would be needed. I would also take a sample of fill water to be tested as well to see if that is where the copper is coming from. If not, then it could be from an older gas heater if the water became corrosive at some point (especially low in pH) or if acid or Trichlor tabs were put into the skimmer.

Richard

 

[OneMom]

Wow!! Thanks for all of the quick replies.

Jason: I got nervous when I read your post, so I just re-ran my tests. We were only able to add 10 ppm of chlorine last night. I'm going to stop & get more this afternoon. Because I haven't put enough chlorine in yet, I didn't test this am, I was waiting to do it tonight after the chlorine had been added. Anyway, last night the FC was at 6, then we added 10. As of 5 mins. ago, these are my results:

FC 13 (I'm testing correctly. Pool water to 10 ml, 26 drops until no longer pink, mult'd by .5)
CC .5 (Barely pink, but not clear)
CYA 50
PH 7.3
TA 110

We run our pump from 7am until 10pm, unless we have algae or are in the middle of a heat wave. During those times we don't turn off the pump. We've had a really HOT summer, it made me nervous to have that pump going 24/7 for 10 days at a time!

We just bought our test kit this year after finding this forum. When we first got the kit (May 25th) our CYA tested at 110!!! We found out here that the high CYA level was due to our using an auto-chlorinator last year. We drained water and by May 31 CYA was at 80. It has slowly lowered over the last three months due to all of the back-washing & splash out. In fact, we've kept such a close eye on it, and it was initially so high, we had to order more of R-0013. We are now almost out of our second 2 oz refill bottle.

We've kept a diary/log this summer with all of our test results. We have been amazed by the small amount of chlorine we lose when the cover is on. We do notice that we have to keep a close eye on the CC level when the cover is on for days at a time. Anyway, now that we used the test kit this summer, we've learned:

Hot & humid days + cover off for days = FC loss of 2-3 ppm per day
Warm days, cool nights, cover on = FC loss of 1 ppm per day

Is this unusual? Do most pool owners lose more chlorine daily than us? Our pool is in the shade in the afternoon (our yard backs up to a woods). Could the combination of afternoon shade & solar cover explain the stability of our chlorine?

I just don't understand how our CYA test could be wrong. Looking back at all of the test results since May, the CYA level has progressively (slowly) lowered over the summer. The only time it increased was when we went on vacation for a week and used the auto-chlorinator. I'm so confused! :?

 

[OneMom]

Chemgeek:

Your post slipped in while I was typing the previous post. Sorry...I wasn't ignoring you.

Just to clarify, as of yesterday, the large, white steps that are built into the pool are coated with the green stuff. The steps now feel slimy. The good thing about the all white fiberglass steps is that it's easy to see what color the stuff is.

We don't have a gas heater, we only have solar panels on the roof. But we did use our chlorinator (pucks) for a week this summer. Would that have been enough to cause the copper problem?

How do we test for metal in the pool & fill water? Do we buy the test or should we take the water somewhere? Is copper harmful to swim in?

Thanks for your help!

 

[Poseidon]

OneMom,
If it's slimy, surely it's algae. Pucks made by HTH do have copper in them. You can buy a test kit for copper, but most people use the local pool store for metal testing. Swimming in copper can cause your fingernails/toenails to turn green, and blonde hair will turn green. Other than that, I don't think it's harmful.

 

[JasonLion]

Yes, your chlorine loss is very low. It would be more common to lose perhaps 15% (cover on) to 40% (cover off) of you chlorine each day to sunlight with a CYA of 50-60 and partial shade. Perhaps your pool is more completely shaded than I imagine from your description.

Having the CYA level go down slowly over the summer is to be expected if you have a sand or DE filter and backwash occasionally.

Your test methods sounds completely correct.

Most pool stores can test for copper. I don't think you have a copper problem. Without a gas heater there is no where for the copper to come from. The worst trouble copper would cause, if you have it, is stains on the walls of the pool and occasionally turning blond hair green. While unsightly and annoying that wouldn't cause any health risks.

Pool pumps are designed to run 24/7. The only problem with running the pump all the time is higher electric bills.

Your experience doesn't fit with what happens for most of us. I am wondering if there isn't some additional factor that we haven't taken into account. I would be very interested if you could get a phosphates test done. Some people have postulated that extremely high phosphate levels could cause something like what you describe. Another possibility is that the CYA test is defective and reading substantially low, but that seems unlikely at this point. Getting a CYA number from a pool store as a double check wouldn't hurt, and anyway they often like to test everything if they test anything.

 

[OneMom]

Okay, I'll take a sample to the pool store to be tested for everything you all suggested.

Thank you ALL for all of your replies.

But, admit it, you all think I'm crazy....don't you?!?

It's funny, because my husband is starting to think I'm loony also. I convince him this summer to start using the BBB method, buy a test kit & stop using the chlorinator. I reassure him that as long as we test regularly and keep everything at the right levels we won't get algae. Then, when we get it, and he asks for an explanation, I just kind of stand there and look all baffled....Duh? LOL

Anyway, I've reassured him that all of you experts will help me to come up with a logical explanation. Now I just need to get him a dose of POP!

 

[OneMom]

Well, we took a water sample to the pool store & had it tested as was recommended here. All of our levels looked great, except for the phosphates.

They told us the phosphate level should be less than 125. Our level is over 300. They had us purchase a bottle of "Phos-X". The bottle listed at $55, but they sold it to us at a 50% discount because it's the end of the season & they're going to be carrying a different manufacturer in the future. Hopefully this product will help us to clear the pool.

I still feel a little confused. Do phosphates cause algae, even if the FC level is okay? Or does a high phosphate level mean that the stuff in the pool isn't really algae?

 

[JasonLion]

Algae requires phosphates to grow. If you get the phosphate level down then algea can't grow. However if you keep the FC level at normal levels then there shouldn't be any algae, phosphates or not. Your phosphate level isn't at all high compared to what I have. Mine is over 4,000, and I simply maintain the chlorine level and all is well. I was wondering if your phosphate level was something like 10,000 or more, which some people claim behaves differently.

Even at "half off" that was a fairly high price for Phos-X. I have seen it on the net for $19. And it is far from clear that it will help, though at this point it might actually be worth trying.

I guess we are back to having a mystery. I'm out of ideas anyway.

 

[OneMom]

The people at the pool store said they have seen a lot of this in the last couple of weeks. They think that it's due to the fact that our area got 8+ inches of rain in five days. The pool store isn't sure if it is algae either.

Yesterday my husband & I brushed down the pool. The ENTIRE bottom was covered with the powdery green stuff. As we would brush, it would dissipate into the water in a large, dark green cloud. We didn't have to scrub to remove it, but the water was so green we were convinced it was algae we were dealing with. When we were done brushing we could barely see the Polaris on the bottom. At that point, the water wasn't dark green any longer, it was a cloudy grayish color that had just a faint tinge of green color to it. Our backwash water is dark green. It hasn't looked like this even when we've dealt with past algae blooms.

Anyway, we still haven't brought FC up to shock level because we added the Phos-X. We didn't lose chloine overnight. The FC level is 14. So, as of this morning, we're back to being convinced we haven't been dealing with algae. This has been a really weird situation. We've lived here for more than 10 years and have never dealt with anything like this.

I hope I haven't exhausted everyone's goodwill here on the board with all of my posts.

I will try really hard not to bug you guys again until next summer!

 

[duraleigh]

This is probably the most puzzling thread I've seen in years. All your test results would indicate that conditions do not exist for algae yet algae seems the most reasonable answer.

It's not clear to me you have determined if this green stuff is slippery when you put it between your finger and thumb.....a clear indication it's organic. If it's not slippery to the touch, it's very unlikely to be algae.....so then what is it? Copper is not likely because it seems you have not been putting copper in your pool and your pH and other results don't suggest conditions for copper to precipitate.

How about the solar cover? Any chance it could be deteriorating and somehow shedding something green?

As Jason said, your results are incredibly atypical to the experiences on this and other forums. The Poos Store's hypothesis of rain makes no sense. IMHO, rainwater has a marginal affect on a well-maintained pool. If the deck is not sloped properly and 8 inches of rain has drained INTO your pool from the surrounding area, then that would be an issue.

I've reread this thread again and have absolutely no clue what is causing your problem.

 

[From_Arizona]

Along the line of a cover starting to deteriorate, I found that the "noodle" material will degrade and cause very fine paticles in the water. If you have pool toys that are the same color, look closely at them to see if they are starting to deteriorate.

 

[chem geek]

OneMom,

If it isn't too late, see if you can save a sample of this green stuff by using a turkey baster or equivalent to suck some up when it's settled to the bottom. Then, let it settle in the jar and slowly pour the water off. See if some between your fingers feels slimy or not. If you have a microscope (even a cheap one), look at it. This just doesn't sound like algae to me, but it does sound like something that the chlorine may eventually bleach out which is why mixing it up in the general pool water seemed to make it fade -- when settled on the bottom where the circulation may be poor (especially if you do not have a floor drain), the chlorine may get locally used up and not react with it as quickly. The theory of a cover or pool noodles deteriorating or possibly something that gets blown in (green pollen?) sounds plausible, though strange.

Did the pool store test for copper? As chlorine gets used up, even from breakdown from sunlight, it will make the pH drop and that will dissolve more copper carbonate precipitate. Copper carbonate looks like the photo in this link, but can look duller and darker if there is copper oxide (which is black as seen in this link). I agree that at low pH this is a long shot, especially since there was no obvious source of copper in your pool.

Richard

 

[dawndenise]

What a mystery! Thinking outside the box...any chance you have prankster kids in the neighborhood....or in the family that might be adding something to your pool????

 

[OneMom]

Hi all, OneMom’s husband here.

I’ve read all the replies to my wife’s post. Thanks for all the input.
Good thoughts about the cover deteriorating and pool toys/noodles in the pool.
We have no toys in the pool and it’s not the cover.
Our pool backs up to woods and is surrounded by TONS of plant life/flowers.
Based on other posts and by the way this stuff does not seem to be growing, I’m convinced it must be pollen.
Mainly because we have not had to add any chlorine in a number of days and it is holding steady. These last few days we’ve been running the filter 24 hours a day.
Yesterday, we brushed the entire pool down and kept the Polaris running for extended times to keep the water as agitated as possible. The greenish powder is being caught in the filter and slowly being removed from the pool by back washing twice a day.

We do have a floor drain and don’t have any copper lines on the pool anywhere. It’s heated using solar panels on the roof, all connected with PVC.

We were mainly trying to figure if this was algae or pollen. As the days go on I’m more and more convinced that it’s pollen.

Thanks again for all your help guys, this is a wonderful resource.

OneDad (I guess)

I've attached a couple pictures of what the stuff looked like two days ago.