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Thread: My battle with algae

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    My battle with algae

    My algea came back less than a month after the last time I shocked the pool. The FC never went below 5.5.

    I think I will just keep the FC around 7 unless someone else has a better idea.

    There may be some circulation problem. It is an oval pool, but the main drain has been sealed off so everything goes through the skimmer. Maybe I should brush the bottom every few days to stir up any water sitting there and not circulating.

    I know people here recommend against the copper based algaecide, but I would like to know more about why I shouldn't add a little of that to the mix. There is no metal in the pool. I don't care if my hair turns green. It might look better green. Just joking, but you have to have very high levels to get green hair don't you?

    The ph is high now because of the shock, but it was around 7.6 when the algae started.

    It has been very hot here. Lots of days it was over 100. Could that have something to do with this?

    FC 23 - shock
    CC 0.5
    ph 8.2
    TA 80
    CYA 45-50
    36 x 18 oval pool, inground, plaster pool.
    27000 gallons
    1 hp pump. Sand filter
    Pool built in 1971.

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    JasonLion's Avatar
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    Re: My battle with algae

    Low copper levels are ineffective against algae, but can still color hair green. Copper levels high enough to be effective against algae are prone to form unsightly and difficult to remove stains on the pool surface, especially when the PH is as high as yours is now.
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    BoDarville's Avatar
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    Re: My battle with algae

    Quote Originally Posted by TomAtlanta
    There may be some circulation problem. It is an oval pool, but the main drain has been sealed off so everything goes through the skimmer. Maybe I should brush the bottom every few days to stir up any water sitting there and not circulating.
    It is always a good idea to brush the pool periodically (~ weekly), algae or no algae. It is possible that there may have been an invisible algae film that remained from your prior shock process or was hidden in some nook or cranny. Brushing will help remove this film and expose the roots of any algae to the chlorine so that it can be completely killed off.

    Next time you shock, I would lower pH to 7.2 before you shock as chlorine is more aggressive as a sanitizer at lower pH levels. Don't overdo it though - make sure pH remains above 7.0. After making that adjustment, ignore pH until the shock process is complete and FC returns below shock levels. At that time, test and adjust pH if necessary.

    Inadequate circulation can also play a role. Just curious: Why was main drain sealed off? A leak or ???

    Edit: Just to clarify, if you are going to shock the pool again, I would brush daily (at least). The weekly brushing is for ongoing maintenance.
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    Re: My battle with algae

    Brushing the pool every other day would be a big help making sure all is exposed to the chlorine.
    You can use ping-pong balls to help see how the circulation is going in your pool. But, it sounds like you know there are some areas not getting circulated. Your brushing is the answer there.

    Running a slightly higher FC is also a good idea. The CYA test is +/- 15 ish so your CYA could indeed be higher and need a higher FC.

    If you insist on using an algaecide, the only one we recommend is PolyQuat 60. If used, it should be added after the algae is killed. It is a preventative, not an algae remover.
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    Re: My battle with algae

    Why was main drain sealed off? A leak or ???
    Leak

    You can use ping-pong balls to help see how the circulation is going in your pool. But, it sounds like you know there are some areas not getting circulated.
    Actually I don't know that for sure. I have watched leaves floating on the surface, and it seems that there is good circulation on the whole surface of the pool. I thought that maybe under the surface in the deep end the circulation was bad.

    Next time you shock, I would lower pH to 7.2 before you shock as chlorine is more aggressive as a sanitizer at lower pH levels
    Any reason not to lower pH today and shock for one more day just to be safe?
    36 x 18 oval pool, inground, plaster pool.
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    BoDarville's Avatar
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    Re: My battle with algae

    Quote Originally Posted by TomAtlanta
    Any reason not to lower pH today and shock for one more day just to be safe?
    pH will read falsely high with FC at shock level. Therefore, if you try to lower it while shocking there is a chance you will over-compensate by lowering it too much
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    Re: My battle with algae

    pH will read falsely high with FC at shock level. Therefore, if you try to lower it while shocking there is a chance you will over-compensate by lowering it too much
    Thanks for the info. I didn't know that. So probably it is not as high as I thought, since I did that test while shocking, and before shocking it was lower. I thought the shock had raised pH.
    36 x 18 oval pool, inground, plaster pool.
    27000 gallons
    1 hp pump. Sand filter
    Pool built in 1971.

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    Re: My battle with algae

    Shocking with hypochlorite does raise the pH and if you read the pH test quickly then with CYA in the water it is likely reading correctly (but if you wait a minute or two you may see the indicator change color). Anyway, you don't worry about the pH when shocking since it is temporary and when shocking to a higher FC level one should usually lower the pH to around 7.2 first anyway.

    As for your options given what does sound like poor bottom circulation (and assuming you've tried pointing returns downwards, though that makes skimming not work as well), you could try using 50 ppm Borates or use Polyquat 60 weekly or (most expensively if your phosphate levels are high) use a phosphate remover. Those options don't have side effects except their cost (I assume you would use a phosphate remover that has a clarifier or you'd use one separately since otherwise it would make a pool cloudy for too long). Or you could just try keeping the chlorine level higher and see how that goes. A higher level will be higher even in poor circulation areas assuming there is some modicum of diffusion and at least some small amount of circulation and hopefully will get above the level that inhibits algae.
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    Re: My battle with algae

    First I'll try higher chlorine level, and brushing the bottom twice a week to stir things up. If that doesn't work I'll try Polyquat 60

    Is this Polyquat 60? It does not have that name but comes up on amazon when I search for Polyquat 60

    http://www.amazon.com/Kem-Tek-311-6-60- ... olyquat+60

    How much of this would I use every week?
    36 x 18 oval pool, inground, plaster pool.
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    Pool built in 1971.

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    Re: My battle with algae

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    Re: My battle with algae

    I cannot see the entire ingredient name. However, from what I can see, that looks right and the concentration of 60% is what you are looking for. The full name of the active ingredient in polyquat algaecide is: poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride]
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    Re: My battle with algae

    It's important to dose the Polyquat 60 once a week per its directions. It does break down from chlorine and is also a mild clarifier so tends to get caught in the filter depending on how much junk there is in the water to clear out. There may be an issue with Polyquat not being as effective at higher CH levels (see this link), but I have Buckman Labs looking into that.
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    Re: My battle with algae

    I think I'll skip the Polyquat 60 for now and experiment with just keeping the chlorine higher plus more brushing to correct for any circulation problem.

    How much chlorine is too much? My CYA measures somewhere around 45-50, but people here say that could be off by as much as 15, so it could be anywhere from 30-65. I got algae growth before when the chlorine never went below 5.5. What if I just kept my minimum chlorine around 8 and my target around 12. Would that do any harm to anything? I don't want to do a drop test every day, so what if I erred on the high side and the chlorine was up around 15 many days. Would that be a problem?

    Does it cost a lot more to keep the chlorine higher? For instance, if you start out on a sunny day at 8 and it goes down to 4 by that night, does that mean that if you start out at 18 it will go down to 14, or will you lose much more?
    36 x 18 oval pool, inground, plaster pool.
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    Re: My battle with algae

    Chlorine loss follows a percentage line somewhat. So at 18 you'll most likely lose 7 to 9 if your usual daily loss is in the 40 to 50% range. Yours is an unusual situation. I would rule out something growing in the pool by shocking and the OCLT test. If you have lights, now would be a good time to pull them and check if anything is hiding behind them. Ladders and steps too.

    Are you sure it's algae? I ask because visible algae usually corresponds to a much greater Chlorine demand. I suppose a circulation dead zone could explain your predicament but it's unusual that it doesn't drop the Chlorine and grab your attention. Probably a good idea to stick with the FAS/DPD test for awhile to quantify your Chlorine demand.
    Bill
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    Re: My battle with algae

    Are you sure it's algae?
    It's brown algae. The guy at the pool store described it to me perfectly. It is kind of like brown dust, but chlorine kills it.

    Yours is an unusual situation.
    If my CYA is higher than I think, or the circulation is bad, then is it unusual?

    If you have lights, now would be a good time to pull them and check if anything is hiding behind them.
    There was a leak at the light, which the leak detector guy fixed. He sealed it with some underwater putty. It is not leaking any more. If it is properly sealed, could algae behind it get into the pool?
    36 x 18 oval pool, inground, plaster pool.
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    Pool built in 1971.

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    Re: My battle with algae

    I have brown dust everyday at the bottom of my pool. It poofs away just by walking near it. Algae tend to cling to surfaces and requires brushing with a little elbow grease. Mustard algae is easier to brush. I never had mustard algae but I don't think it dislodges just from a current. When you say "Chlorine kills it", do you mean that it disappears on it's own without vacuuming or brushing?

    My main point is that once algae starts there's warning signs. Increased Chlorine demand is your first indicator. The OCLT test is darn near foolproof to prove or disprove if there's an algae problem. Even if algae is hiding somewhere the OCLT will alert you to a problem.
    Bill
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    Hayward S166T 100 lb sand filter

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    Re: My battle with algae

    This stuff poofs away if I run my hand over it, but not if I walk near it. There was a lot of it all over the pool. When I vacuumed it, it came back a day or two later. When I shocked it, it turned a lighter color and then when I brushed it, it went away for about a month, until the chlorine got lower, and then it came back. I am pretty sure it is some kind of algae.
    36 x 18 oval pool, inground, plaster pool.
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    Pool built in 1971.

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    Re: My battle with algae

    Quote Originally Posted by TomAtlanta
    This stuff poofs away if I run my hand over it, but not if I walk near it. There was a lot of it all over the pool. When I vacuumed it, it came back a day or two later. When I shocked it, it turned a lighter color and then when I brushed it, it went away for about a month, until the chlorine got lower, and then it came back. I am pretty sure it is some kind of algae.
    Is it just on the bottom? If so, it sounds like fine dirt to me. Do the OCLT. You'll know for sure.
    Bill
    18'X4' 7600 Gal AG
    3/4 HP Pentair Pump
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    Re: My battle with algae

    Is it just on the bottom? If so, it sounds like fine dirt to me. Do the OCLT. You'll know for sure.
    It is gone now, since the last shock. When it was here, it was on bottom and sides. When I did the OCLT after the last shock there was no chlorine loss over night. If and when it comes back I will do the OCLT before I do the shock.
    36 x 18 oval pool, inground, plaster pool.
    27000 gallons
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    Pool built in 1971.

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    Re: My battle with algae

    Quote Originally Posted by TomAtlanta
    Is it just on the bottom? If so, it sounds like fine dirt to me. Do the OCLT. You'll know for sure.
    It is gone now, since the last shock. When it was here, it was on bottom and sides. When I did the OCLT after the last shock there was no chlorine loss over night. If and when it comes back I will do the OCLT before I do the shock.
    Let's drink to it not coming back.
    Bill
    18'X4' 7600 Gal AG
    3/4 HP Pentair Pump
    Hayward S166T 100 lb sand filter

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