Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 6 of 6

Thread: CYA much too high, algae -- drain/refill or SLAM?

  1. Back To Top    #1

    Join Date
    Jul 2014
    Location
    Livermore, CA
    Posts
    3

    CYA much too high, algae -- drain/refill or SLAM?

    The challenge:

    Thought I had chemistry under control, but a week away and returned to find crawler hung up on thermometer cord. Bottom of pool covered in green slime. This tells me that I have had an algae bloom, but was simply vacuuming it up. Need to kill this stuff off for good.

    Challenge: 45,000 gallon pool, CYA is probably north of 150 (scale on test kit tube doesn't go that high; my best guess). SLAMming would require enormous amounts of chlorine (25 gallons at 11% concentration at current CYA levels); perhaps too much. Ideally I would drain and refill, but we're in the middle of a drought here in northern CA and such things, while not yet prohibited, are not encouraged. Further, if I drain and refill, I do not know how to eliminate whatever algae might be in the cartridge, or how to kill whatever is left stuck on the pool walls.

    So: SLAM or drain/refill and deal with the walls and cartridge? Any and all suggestions appreciated; I'm a rookie pool owner. Many thanks.
    --
    Mark
    early 1970s 45,000 gallon IG plaster
    cartridge filter
    Pentair pump, single speed

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: CYA much too high, algae -- drain/refill or SLAM?

    Welcome to TFP!

    Drain and refill is by far the better option if it is at all possible. You will still have to fight algae once the pool is refilled, but doing so will be much much simpler. You probably don't need to do a 100% drain and refill, draining 75% is probably enough.

    You might want to do a CYA test with dilution to get a better handle on just how high your CYA level really is. To do this, mix equal parts of pool water and tap water, do the CYA test normally with that mixture, and then multiply the result by two. You lose a lot of precision that way, but it will tell you if the level is 100, 150, or 200+.
    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

    Join Date
    Jul 2014
    Location
    Livermore, CA
    Posts
    3

    Re: CYA much too high, algae -- drain/refill or SLAM?

    Jason:

    Many thanks for the quick response

    Quote Originally Posted by JasonLion View Post
    Welcome to TFP!

    Drain and refill is by far the better option if it is at all possible. You will still have to fight algae once the pool is refilled, but doing so will be much much simpler. You probably don't need to do a 100% drain and refill, draining 75% is probably enough.
    I'm leaning this way. But if I drain and refill, do I have to do anything to any algae that might be on stairs/walls or in the cartridge?

    You might want to do a CYA test with dilution to get a better handle on just how high your CYA level really is. To do this, mix equal parts of pool water and tap water, do the CYA test normally with that mixture, and then multiply the result by two. You lose a lot of precision that way, but it will tell you if the level is 100, 150, or 200+.
    I'll give this a try. I might also do a CYA test on the tap water just to get a baseline number, as that's what will go in the pool.

    With the current drought, I'm sure my neighbors will not be happy with me. But it's getting to the point where I can't put enough chlorine in to keep things sanitized.
    early 1970s 45,000 gallon IG plaster
    cartridge filter
    Pentair pump, single speed

  4. Back To Top    #4

    TFP Guide

    Kiss4aFrog's Avatar
    Join Date
    May 2013
    Location
    Hudson, WI
    Posts
    2,602

    Re: CYA much too high, algae -- drain/refill or SLAM?

    Welcome to the forum

    Drain, refill and then SLAM to get rid of the algae. http://www.troublefreepool.com/conte...tain-shockingl

    There shouldn't be any CYA in your tap water.
    '70s IG Vinyl 32K gal, Lazy L, Hayward SuperPump 1.5hp 120V, S240 Sand Filter W/DE
    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
    1979, 275gal Conway Emerald Spa P-100-2, ES-2 Spa Pack, bromine floater, indoor
    TF-100, Best test kit - TFTestkits.net
    Please help keep the lights on, become a TFP Supporter!

  5. Back To Top    #5

    Join Date
    Jul 2014
    Location
    Livermore, CA
    Posts
    3

    Re: CYA much too high, algae -- drain/refill or SLAM?

    Quote Originally Posted by kiss4afrog View Post

    Drain, refill and then SLAM to get rid of the algae.
    Once the pool is drained, should I not try to clean off algae from steps, etc.? Should I try to "shock" the cartridge before refilling the pool?
    early 1970s 45,000 gallon IG plaster
    cartridge filter
    Pentair pump, single speed

  6. Back To Top    #6

    TFP Guide

    Kiss4aFrog's Avatar
    Join Date
    May 2013
    Location
    Hudson, WI
    Posts
    2,602

    Re: CYA much too high, algae -- drain/refill or SLAM?

    It never hurts to get everything done as early as you can. While draining or filling thoroughly clean the steps or ladders, if you have a light the light and niche and pulling the cartridge and cleaning it are always good ideas.
    You don't need to shock the cartridge just a good cleaning as when you SLAM (shock) the pool you will be running more than enough chlorine through everything !!
    '70s IG Vinyl 32K gal, Lazy L, Hayward SuperPump 1.5hp 120V, S240 Sand Filter W/DE
    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
    1979, 275gal Conway Emerald Spa P-100-2, ES-2 Spa Pack, bromine floater, indoor
    TF-100, Best test kit - TFTestkits.net
    Please help keep the lights on, become a TFP Supporter!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •