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Thread: SWG plaster pool....couple basic chemistry questions

  1. Back To Top    #1

    Join Date
    Apr 2016
    Youngsville, LA

    SWG plaster pool....couple basic chemistry questions

    Finally got my new salt cell in, so therefore I can adjust my CYA now that I can produce chlorine at a sufficient rate. My current chemistries are below:

    pH 7.4 - (Can I keep this around 7.2-7.4 range or is that too low?)...I have a little scale buildup and was trying to keep it on the lower side to help prevent that.
    TA 40 - (I was going to bump this up to 60 or should I take it to 70?)
    CYA 35 - (I was planning on bringing it up to 70 and target 5 for FC.)
    CH 140 - (Should I bump this to 200 or 250 beings it's a plaster pool?)...Just bought 12 lbs of Calcium Hardness yesterday

    15k Gallon In Ground Saltwater Gunite Pool and Spa w/ Overflow
    Dolphin Nautilus Plus Pool Cleaner
    Main Filter Pump - 1.5HP Pentair Whisperflo connected to Triton II Sand Filter
    Spa Pump - 2HP Pentair Whisperflo w/ 2HP Polaris Spa Air Blower
    Resilience PSC3 SWCG

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

    Re: SWG plaster pool....couple basic chemistry questions

    I would only bump TA to 50 for now and see if your PH stays stable. CYA 70, yes. CH at least 250, 300 is better. Keep PH between 7.6 and 7.8 is better.

    Here is the SWG water chemistry summary page, Pool School - Water Balance for SWGs

    For your scale, you need to manage your CSI. It needs to be kept slightly negative, between -0.1 and -0.3. This is good for your plaster, your SWG and prevents scaling. Poolmath calculates your CSI when you input your test results. Tweak PH, TA and CH to change the number. Any combo that results in a desired CSI number is fine, but having TA higher than 60 or so will often result in rising PH, so it is preferable to keep TA low (50-60) and avoid running waterfalls and bubblers too much because they also cause PH to rise.

    More here, Pool School - Calcium Scaling
    And here, Langelier and Calcite Saturation Indices (LSI and CSI)
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