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Thread: Backwashing with Mustard Algae

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    Cherie's Avatar
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    Backwashing with Mustard Algae

    Hi all. While I'm waiting on my TF-100 kit to arrive, I needed ask a question about backwashing.
    Before finding TFP, and at the advice of 3 pool stores, we backwashed several times in June, after going through the process to kill the mustard algae (which STILL isn't dead). So now that we know how to do this right, I need to ask a couple of questions still.

    #1: Is it necessary to b/w after doing the high fc kill, as well as vacuum to waste during the process?

    #2: I wanted to lower our CYA to about 20-30 before starting the kill this time, so I don't have to use as much chlorine. But if we're going to be vacuuming to waste and backwashing afterward anyway, will another b/w and vac'g to waste during the kill lower my CYA too much? Or should I just leave things as they are and do the kill FIRST, then, see where my CYA is after the kill?

    #3: I also wanted to lower our pH to about 7.2 before starting the kill. I had it to 7.3, but it went back up to 7.5 yesterday! TA is holding steady at 100.

    So our plan of attack is to lower the CYA to 20-30 (sump pumping the water onto our VERY dry, VERY cracked yard), then lower the pH back down to 7.2ish, then start the attack.

    Current readings: ran out of kit stuff, so using strips

    FC: Looks to be over 5 a little, but not close to 10
    TC: same
    pH: 7.3ish (strip) .. 7.5ish drops
    TA: 100 (drops)
    CYA: 30-50 range (strip) .. Leslie's consistently testing at 40.

    I can't differentiate the colors on those strips very well.

    Any advice would be greatly appreciated. This site is great!


    Cherie
    32x16 buried Doughboy, 4' shallow - 7' deep
    Pentair Dynamo 1 hp, 2-speed - Pentair 150# SD40 w/zeolite (75#)
    One skimmer/two returns/Aquabot Turbo T2

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    JasonLion's Avatar
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    Re: Backwashing with Mustard Algae

    You shouldn't need to backwash or vacuum to waste at all. Lowering your PH is also not critical.

    Lowering your CYA level has advantages and disadvantages. Lower CYA means less chlorine to bring the pool up to high shock level, but more chlorine lost to sunlight while holding the pool at high shock level.

    My sequence for killing persistent mustard algae is to first shock to normal levels until all visible signs of the mustard algae are gone. Then maintain high shock FC levels continuously for at least 24, and preferably 72, hours. During this entire process it is very important to brush the entire pool at least once a day paying particular attention to areas with bad circulation, like around ladders and inside lighting niches. Also, all pool tools and toys should either be soaked in the pool for a couple of hours while at high shock or rinsed with a dilute bleach solution.

    The most common mistake is to miss some hidden area, like behind or inside ladders or inside light niches. The algae can hide out there and then come right back when the FC level comes down.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3
    Cherie's Avatar
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    Re: Backwashing with Mustard Algae

    Thanks Jason. I guess I was just thinking in terms of after the algae is gone, I wanted to be able to just keep my FC at around 3-4 ppm (with 20-30 cya), instead of 5-6 now (with the 40-45 cya). But given that maintenance is now so easy anyway, now that we've gone BBB, I shouldn't be complaining!

    I've been brushing the pool twice daily, usually in the morning (just because I hate seeing the "dusty spots") and again in the evening, after I add my daily dose of bleach. I also took the ladder out (if I could figure out how to add my avatar, I could show you our setup) when we did the Yellow Out "treatment" and sprayed full strength bleach on every inch of it - except in the cavern at the bottom step that is screwed together. But I tried to get the bleach in there as best I could. We didn't allow any toys back into the pool and I washed all our swim stuff in hot water - with a very light splash of algaecide. But it was all for naught, because we didn't have the right instructions each time....UNTIL NOW!

    I don't relish the idea of spending more money on Yellow Out - since we don't have a serious infestation, unless you think it will help.

    I used to get so excited to walk into our back yard and admire our new pool, all nice and clean. But this sandy stuff has really gotten me down - given that we've been dealing with it since early June now We had a "professional" pool guy come out on July 2 and told us it wasn't algae - it was dust. So I haven't done anything but regular maintenance since then, except the extra brushing. But we don't have DUST in Wylie, we have clay, ugly gray clumpy clay (trying saying THAT one 5 times fast ) So it took me awhile to convince my DH that the pool guy was wrong. He also told us to mix a couple of chemicals together in a bucket before adding them to the pool. That was MY cue that he was clueless (thanks to y'all).

    Once we start the shock, how often do we need to test the water to make sure we're staying at 24ppm FC - and should I test in the dark morning hours ? It sounds like it might be better for me to leave the ladder right where it is, so the 24ppm can disinfect it. I'll go back and review all the pages I've printed and notes I've taken so I don't have to ask these kinds of redundant questions!

    Thanks for your help!
    32x16 buried Doughboy, 4' shallow - 7' deep
    Pentair Dynamo 1 hp, 2-speed - Pentair 150# SD40 w/zeolite (75#)
    One skimmer/two returns/Aquabot Turbo T2

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    JasonLion's Avatar
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    Re: Backwashing with Mustard Algae

    Many people confuse mustard algae with dust. It can be a very difficult to tell them apart sometimes. A serious case of mustard algae will grow on the walls of the pool and dust won't do that. But with a milder case it isn't always obvious. Mustard algae looks like this:

    With experience it becomes obvious which is which, the picture isn't always good enough to give you the complete idea, but if you haven't seen it before it is easy to confuse. The other test is that mustard algae will appear to almost entirely go away at normal shock levels with brushing, while dust will continue to appear at the same rate.

    Dust can get blown in from very far away. Dust from Africa reaches the East Coast sometimes.

    Dead green algae can also settle on the bottom of the pool, and look rather like dust and mustard algae sometimes, particularly when you are just under the correct FC level. This is most common at high CYA levels and with SWGs.

    I almost never recommend Yellow Out. It is only really worth it when you have very high CYA levels and some strong reason not to lower them.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Backwashing with Mustard Algae

    I am sorry if I'm not understanding here, but what exactly do you mean when you say "mustard algae will appear to almost entirely go away at normal shock levels?" What are normal shock levels? Does that mean you shock the pool with non-chlorine shock versus using chlorine shock? Because chlorine shock will obviously raise your free chlorine levels above normal, correct?
    20,000 in-ground pebble-coat pool with 60sf Jandy DE filter, Pentair Variable-Flow pump, Goldline Aquarite SWG, Dolphin Premiere robot, passive solar heating.

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    JasonLion's Avatar
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    Re: Backwashing with Mustard Algae

    Shock the pool normally according to the directions at Pool School (with chlorine) and mustard algae will vanish for as long as your maintain the high FC levels. But then the mustard algae will come back when you lower the FC level back down. By "normal shock levels" I mean using the number from the Shock FC column in this chart.

    To completely kill mustard algae you often need to raise the FC level higher than that, to what I often call mustard algae shock level or high shock level.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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