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Thread: New Member - Questions on Algae and High CYA

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    Join Date
    Jun 2016
    Concord, NH

    New Member - Questions on Algae and High CYA

    Hello, first time poster, long time pool addict...

    My wife and I purchased a house two weeks ago that has a 26' above ground pool. Previous owner bought the pool used, had it installed professionally with a new liner. The day we closed (5/26), we pulled off the cover, filled with water to the skimmer, and fired up the pump. Good circulation, everything worked, a few equipment drips here and there but overall I was pretty satisfied. The water was green, with visibility about a foot below the surface. Having owned a pool before, I took the tact of adding some liquid shock (2 gallons), adjusting the PH, and seeing what would happen. As the week progressed, the algae got worse. I added two additional gallons of shock, and 6 1lb packs of granular shock, during the first week. The two way test kit showed plenty of chlorine, ph acceptable at the end of the week. This past weekend I opened the sand filter up and found the stand pipe cracked. We deemed the existing pump (1.5 HP, bearings were very noisy), housing (cover cracked) and broken filter not worth fixing; so I purchased and installed a new 1HP 18" Hayward Pro filter/pump combo. I used three 25lb bags of ZeoSand, backwashed, and set it on filter. Initial PSI was at 16. Aimed the eyeball down and to the right, creating a lazy counter clockwise spin to the surface. Beginning Monday, using the WalMart 10% pool bleach, I added: 3 gallons Monday, 2 gallons Tuesday, and 2 gallons Wednesday. On Monday, I ordered a TF-100, which was delivered yesterday. Last night I did two tests, TC and CYA. TC was at 35, and CYA was between 90-100. I tested again this AM and came up with the same results.

    Based on the TC/CYA chart, I need FC around 40 to be at shock levels. This verifies my theory that when I began blindly adding chemicals the CYA was very high to start, and the shock added to it, creating the problem I have now. I simply wasn't adding enough liquid chlorine to bring it up to shock level, and that is why the algae is now worse than when I started.

    I am contemplating draining the pool and refilling. A local pool water delivery company can deliver 6K gallons for $275. It is public drinking water from a local municipality. I have a well with high iron, and between battling an iron problem in the pool and killing my well, it seems that $275 may be a bargain. This should bring my CYA down to a more manageable 50-60, and rid the pool of some seriously green water. Based on the Pentair pool volume calculator, a 26' round pool at 1.5' depth is just at 6K gallons.

    So, my plan is: drain 1.5' of water (leaving 2.5' in the pool), fill with new water, circulate for two hours, and take all new baseline measurements using my TF-100 test kit, and go from there. The only downside I can see to this is wrinkling the liner, however, I've read that leaving 2.5' in the pool should be ok.

    Am I on the right track? Thanks in advance for any input

    15K gallon vinyl-lined above ground, Hayward S180T92S 18 inch Pro Series Filter (new June 2016), 75lbs ZeoSand (150lb sand equivalent).

  2. Back To Top    #2
    Mod Squad
    Join Date
    Aug 2012
    DFW, TX

    Re: New Member - Questions on Algae and High CYA

    Welcome to TFP!

    Nice job reading up. That is a great plan. We recommend leaving at least a foot of water in the shallow to avoid liner shifting, shrinking, wrinkling, etc.

    Did you order a TF100 from yet?
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Join Date
    Jun 2016
    Concord, NH

    Re: New Member - Questions on Algae and High CYA

    Had the water delivered yesterday. Put 128 oz of 10% in and ran the pump. Test results last night:

    FC 37.3
    CH 125
    TA 50
    CNA 60
    PH 8.2

    Measured FC this am and got 30, for an overnight loss of 20%. Backwashing every 12 hours or so when psi increases 25%.

    Going to procure some baking soda & muriatic acid for some adjustments

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    TFP Guide
    Catanzaro's Avatar
    Join Date
    Jul 2014
    Howell, New Jersey

    Re: New Member - Questions on Algae and High CYA

    Nice Job. You are getting the hang of everything. Can you post some pictures? Please lower PH in increments. Only use half of what pool math states with Muriatic Acid (MA) and then next day after testing add a little more, if needed. TA seems a little low as well and wondering why the PH is high as your TA is very low. CH is fine. Please remember to brush the pool regularly to break up any algae on the walls. Remember that all of the 3 criteria's must be met before you are finished with the SLAM. Your CYA at 60 is fine for now and over time, the levels will drop. I see about a 20 ppm drop each year and keep mine between 40-50, which only requires a 1 ppm higher FC daily level.
    14,700 gallons IG Pool Vinyl Liner - Octal Circulation System
    Hayward Pro-Series 350 LB. Sand Filter Model # S270T - 2" Plumping
    Frog Mineralizer System (EMPTY) - Hayward Super Pump 2 HP Model # k48m2n111
    Pool Company tests water (NO LONGER) TF-100 TEST KIT
    Date of Build is 11-2013

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    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: New Member - Questions on Algae and High CYA

    The trucked in water won't get rid of your grows right back. However, if you replace enough, it will help with the iron in your water.

    Do you have a softener that you can use as your fill source?
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  6. Back To Top    #6
    smforte's Avatar
    Join Date
    Sep 2013

    Re: New Member - Questions on Algae and High CYA

    Also, I'd wait on adjusting the PH since the ph test is unreliable at higher FC levels pat 10 ppm.
    Montgomery, AL
    27000 16 x 36 IG, Vinyl, Grecian, Hayward Sand filter, 1 HP Pentair whisperflo motor, Aqua Genie filter not by choice, no extra jets, Dolphin s300i robotic cleaner,Taylor K 2006 test kit, speed-stir which I couldn't live without!

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