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Thread: Best Chemical Balance For A Salt Water Pool with Iron Issues

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    Best Chemical Balance For A Salt Water Pool with Iron Issues

    I just did an inpool (no drain) AA treatment over the weekend as we are having guests and am asking for advice.

    What would be best assuming the following:

    The pool has iron issues due to airborne volcanic dust and red clay born particles.
    The pool is maintained with Jack's Magic Purple Stuff at 20 ppm using test kit, tested once week at a minimum if no high winds.
    The pool has an automatic acid feeder.
    Algaecide 60 is used weekly per instructions.
    The alkalinity never drops below 80 if left uncovered and is often at 90 if the cover is used nightly.
    Because of trade winds the normal temperature is 78F if left uncovered during the day or 82F to 84F if left covered, assume 78F.
    Most forum advisers seem to recommended to control iron issues it is best to keep the pH at 7.4 or below it is now maintained at 7.3, it was higher before but iron stains develop more quickly.

    Using the pool calculator with the following parameters the CSI is negative 0.42.

    FC 5 (used to be 8 but JasonLion answered a post I wrote and stated that this was too high and not necessary as I had no algae issues)
    pH 7.3 (was 7.6)
    TA 80 to 90
    CH 425 (over this number creates scaling issues in the cell)
    CyA 75
    Salt 3200 -3400 (currently 3200)
    Borates 0 (Dog)
    Temp 78F (sometimes 82F to 84F)

    Should I just let the pH go to 7.6 and have a negative CSI of 0.15 and live with the significantly faster build up of stains or up the TA to 120 and and have a negative CSI of 0.20? Other ideas would be welcome.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    Mod Squad jblizzle's Avatar
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    Re: Best Chemical Balance For A Salt Water Pool with Iron Is

    Remind us again the type of pool (add your pool info to your signature).

    I am assuming it is plaster/aggregate if you are concerned about CSI. Even your -0.42 is within range, so why mess with anything?

    I will say if you are maintaining your FC correctly, the Algaecide 60 is not needed ... save yourself some money.
    Jason, TFP Moderator
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    Re: Best Chemical Balance For A Salt Water Pool with Iron Is

    jblizzle,

    Yes plaster, but at a 0.42 negative CSI would the finish not corrode faster?

    Added signature, thank you.

    Thank you for your quick reply.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    Mod Squad jblizzle's Avatar
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    Re: Best Chemical Balance For A Salt Water Pool with Iron Is

    Maybe slightly faster? But, I am no expert

    I just know that < -0.6 is what is generally suggested as a problem.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: Best Chemical Balance For A Salt Water Pool with Iron Is

    jblizzle,

    I will try no Algaecide 60.

    And yes it would be interesting to know how much faster the surface might deteriorate.

    Thank you
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    JasonLion's Avatar
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    Re: Best Chemical Balance For A Salt Water Pool with Iron Is

    Surface deterioration is not generally observable until the CSI goes down to somewhere around -1.0. However I have never seen anyone test for extremely slow rates of deterioration, so I am not completely sure what levels that starts at. As a general rule anything over -0.5 or -0.6, depending on who you ask, is alright as long as there is no plausible way for it to go down from there. If you are using trichlor you don't want CSI down anywhere near that low, as trichlor will drive the PH and TA down if you aren't paying attention. But is a SWG pool the primary risk is that CSI would drift up if the acid feed failed, so there is no need to maintain "headroom" on the low end.
    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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