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Thread: Removing algae stains with winter cover on due to low CYA

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    Join Date
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    Removing algae stains with winter cover on due to low CYA

    Hi all. I've ready many threads here about organic algae/leaf stains, but would like to solicit some thoughts about my approach to solving my issue.
    -Mainly, with CYA low, i'm leaving my cover on and running the pump 24/7 to deal with this staining to protect chlorine from the sun. don't know if the sun is a vital component in fighting algae in addition to chlorine... as the stains aren't fading much despite running a week of higher chlorine (for current CYA level) with pump 24/7.

    ~*~*~*~*

    I did a bad thing last year, when closing the pool. I had recurring bouts of what I thought was mustard algae, so closed the pool with a bit of that on the pool walls, and didn't bother bringing it up to shock level as I figured I'd open and have to SLAM it anyway in the spring. Come spring time (with an early warm up, then few weeks of freeze, and then now finally consistently warm weather), I've opened up the pool to a massive algae bloom! I've pulled out bags and bags of algae slime and seaweed?!

    It's been about a week now of running the filter 24/7 at shock level and the stains are still there. I had drained the pool last year to bring down my CYA level, and ironically, I opened up the pool to a CYA of probably less than 15 (no good way to tell). As such, I've kept my loop loc dark mesh cover on and brought my chem levels up and have kept it on, whilst running the pool filter and my tiger shark vacuum underneath the cover again and again.

    I'm bringing up CYA levels using dichlor and keeping a shock level of about 12ppm. My pool is rather large, at 48,000 gallons so chemical costs are pretty costly. My regular supply of chlorine comes from 12.5% bleach (they sell 4 gallon packs at BJs wholesale). The pool is otherwise balanced:

    CH: 250
    FAC: 12
    CYA : 15? (trying to raise)
    TA: 110
    pH: 7.2
    No metals

    As an aside, I left a trichlor puck directly on the stains for about an hour and the stains bleached off, so they're definitely organic (and most probably from my algae bloom). It's been a week though at shock level and the stains aren't really fading.

    The wife is furious that we couldn't swim in the pool for Memorial Day... "Just hire someone" she says... and boy, do I NOT want to do that! Help!!
    48,000 IG Gunite - Pool built 1999
    Hayward DE-6000 Filter w/ C-1100-SEP Separation Tank
    Hayward Super Pump 2.0-HP : SP1615Z1MEG
    Hayward H-Series heater
    TF-100 Test Kit

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    Texas Splash's Avatar
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    Re: Removing algae stains with winter cover on due to low CYA

    Well, since you know you have algae, you know a TFP "SLAM" is in order (link below). There's just no way around that. But your CYA is much too low. It must be at least 30 to adequately protect your FC and your pool liner. In addition, you should leave the cover off during the SLAM. It's important for the water to "breathe" and for the sunlight to hit the water to enhance oxidation of your CCs. So I would recommend going back to the SLAM basics. Just review the page, follow all the instructions listed there, and maintain your FC and CYA accordingly. If the pool is as bad as you described, it may take a while, but it will work. Take the wife out to dinner and apologize repeatedly and you should be okay.

    Oh, and keep a close eye on that DE filter. The psi should increase by 25% quite rapidly requiring additional backwashes which will in-turn lower your CYA over time.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    Re: Removing algae stains with winter cover on due to low CYA

    Thanks Texas Splash. The thought was that keeping the cover on would help me hold the chlorine while I work to get the CYA up. At the low level that it's currently at, the sun would burn it up pretty quickly.

    Also, it was thought to be a good move for my wallet, since at lower CYA levels, the FC shock level would not need to be as high. I was thinking that this may be a faster approach to getting the stains to fade since there's more chlorine fighting power this way...

    Am I thinking about this wrong? Is the "oxidation of cc's" more important than the high free available chlorine level (relative to CYA at 30)?

    (also, my pool is gunite, so no liner to worry about. All the algae is already gone, its just the stains that are left. lastly, I have no "waste" valve, as I have a separation tank that is plumbed back into the pool returns, so the only way to reduce CYA is to drain water (last year's ordeal).)
    48,000 IG Gunite - Pool built 1999
    Hayward DE-6000 Filter w/ C-1100-SEP Separation Tank
    Hayward Super Pump 2.0-HP : SP1615Z1MEG
    Hayward H-Series heater
    TF-100 Test Kit

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    Texas Splash's Avatar
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    Re: Removing algae stains with winter cover on due to low CYA

    With no liner or worries about swimmers in the water, I suspect you have a little more flexibility with how you manage your FC/CYA ratio in an effort to reduce the stains. The cover certainly will help to protect FC, thereby allowing CYA to work its way up slowly. But you should let the sun hit the water for at least an hour or two each day just to purge the CCs. If the CC are not oxidized, then they remain in the water and become counterproductive to your effort. All-in-all, you seem to have a good working knowledge of your pool and system operations, so press-on with your SLAM and I hope the elevated FC level helps to eliminate your stains much in the same way the trichlor puck did.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    Re: Removing algae stains with winter cover on due to low CYA

    Thank you again Pat. It's a pain because of all the anchors, but I think I can manage to pull the cover off for a few hours in the early evening.

    Do you think 7pm'ish Northeast summer daylight is good enough to oxidize those CCs?
    They're definitely there (~0.5-1 CC, i'm testing at 5ml level so each drop is worth only 1 to conserve FAS/DPD test solution) as my TF-100 test tells me.
    48,000 IG Gunite - Pool built 1999
    Hayward DE-6000 Filter w/ C-1100-SEP Separation Tank
    Hayward Super Pump 2.0-HP : SP1615Z1MEG
    Hayward H-Series heater
    TF-100 Test Kit

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    Texas Splash's Avatar
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    Re: Removing algae stains with winter cover on due to low CYA

    All you can do with your cover is what you can based on your schedule. A little sunlight is better than none at all. Testing at the 5ml mark is just fine when all you need is a quick verification without as much precision. Good call.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    Join Date
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    Re: Removing algae stains with winter cover on due to low CYA

    Thanks for all the help thus far, Pat.

    I'm still proceeding with the pool covered at shock level, and removing the cover in evening, but the stains are still all across the pool and don't seem to have lightened at all (still green tint). If the stains are going to be there a while and I just need to give it time, is there a need to keep the pool at shock levels? i.e. could I just keep it slightly above normal FC and it should fade sometime during the swim season?

    Not sure if the organic stain is comprised of "live algae" or just the remnants of the former.
    48,000 IG Gunite - Pool built 1999
    Hayward DE-6000 Filter w/ C-1100-SEP Separation Tank
    Hayward Super Pump 2.0-HP : SP1615Z1MEG
    Hayward H-Series heater
    TF-100 Test Kit

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    Mod Squad pooldv's Avatar
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    Re: Removing algae stains with winter cover on due to low CYA

    It doesn't need to be all the way to shock level and brushing helps. Yes, it will take some time, weeks.
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