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Thread: Low pH & Alk, High CYA -- where do I start?

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    wollerd's Avatar
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    Low pH & Alk, High CYA -- where do I start?

    Hi. Iím a long time lurker and a first time poster. A short history. I bought a home late last year with a 20x40 in-ground vinyl pool, 2 skimmers and 2 returns. We also have a separate spa (360 gal). TroubleFreePool has been a tremendous resource and Iíve gone the BBB route with the spa. I want to do the same with the pool. The previous owner didnít pay any attention to balancing the water; he just threw in enough granular chlorine to keep it clear. After correcting a leak in the spa plumbing and witnessing the deterioration inside these pipes, Iím rather concerned about the pool which is a few years older. Anyway, I digress.

    Since December, Iíve been in discovery mode reading through Pool School and perusing many forums. Iíve learned a lot and have a pretty good idea of where I am and where I need to go. Iíve just taken the cover off of the pool for the first time. The water level is above the eyeballs and below the skimmer. The water is clear and the liner is lined with green algae. Water temp is 55. I took the chemistry using the TF-100 test kit with the following results: FC=0, pH < 6.8, TA=20, CH=90, CYA=70. The weather outlook is for sunny and 70s for the next couple days and then some severe T/S and rain for a couple days.

    My most pressing question is where do I start? Should I bring the water level up and start the pump, brush and shock to kill the algae? Or, drain 35-55% replacing with fresh to bring the CYA down? And, I presume that the pH/TA need immediate attention. Please point me in the right direction and thanks for all youíve already done.
    St. Louis, MO
    33K gal, IG vinyl, 2.2 SFHP WhisperFlo pump, Tagelus 325# TA-60D 3.1 sqft sand filter (24.5" diameter), MiniMax Plus 400M heater, TigerShark robot

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    Mod Squad Bama Rambler's Avatar
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    Re: Low pH & Alk, High CYA -- where do I start?

    You're right about the pH & TA. I'd work on that after you raise the water level so you can get it circulating. Once you raise the water level to the proper height you may find that the CYA is about where you want it.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/ľhp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    linen's Avatar
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    Re: Low pH & Alk, High CYA -- where do I start?

    Welcome to tfp, wollerd

    Bama has you covered!
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Mod Squad woodyp's Avatar
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    Re: Low pH & Alk, High CYA -- where do I start?

    Yep. Fill it, circulate it, shock it, initiallly take PH to 7.5ish, Fix the TA in range and adjust your PH again.
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
    2 Speed Hayward Power-Flo Matrix 85 g.p.m. 22" 250lb. sand filter hard plumbed
    Pool Rover Jr., Pool Blaster Max, Diver Dave TF100 Test Kit/Speed Stir
    Margaritaville Frozen Concoction Maker, Liqour Chiller, & Drink Mixer & Party Tub----Collect 'um all!

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    wollerd's Avatar
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    Re: Low pH & Alk, High CYA -- where do I start?

    Thank you all for the quick responses and insight. I've got the water level up and the pump/filter running. The pH=7.5, TA=130, CYA=40 (at ~55į). I added liquid chlorine (12.5%) morning and afternoon yesterday and again this morning to shock level (according to the Chlorine / CYA Chart). I thought it would speed up the "kill" by brushing the pool but that stirred up a lot of green. I probably should have just vacuumed that to waste I've gone through 11 gallons of chlorine and each test has shown .5 - 1 ppm FC prior to the next dose. It's supposed to rain all week with T/S on Wednesday... No real questions here but any advise or encouragement would be greatly appreciated.
    St. Louis, MO
    33K gal, IG vinyl, 2.2 SFHP WhisperFlo pump, Tagelus 325# TA-60D 3.1 sqft sand filter (24.5" diameter), MiniMax Plus 400M heater, TigerShark robot

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