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Thread: Need Some Help With Reading PH

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    Need Some Help With Reading PH


    Great site! Just got my TFTest kit and I am having trouble reading PH. Overall, it is pink and I think it is probably around 7.6 to 7.8 or higher, but it doesn't really match up well with any of the colors on the chart because it is so faint (It's definitely not yellow, and not purple). Also, depending on the angle that I am holding the test cylender, it seems to be a different shade of pink! Maybe I am just slightly color blind???

    If I were to add more than 5 drops of the phenol red (to try and make the solution darker), would that also skew the numbers?

    I have been reading for a while and from what I have gathered, it looks like I should add some acid to lower the PH (if it is indeed 7.8 or higher). Will adding acid also lower the TA?

    Here are my readings:

    PH 7.6 - 7.8 (not really sure)
    FC 10
    CC 1
    TC 11
    TA 170
    CA 400 (We have very hard water here. I have a vinyl pool, so I don't think CA is too important.)
    CYA 80

    I also know my CYA is a little on the high side, but is it anything to worry about right now?

    Slightly off topic, I tested my tap water as well and got the same PH of 7.6 - 7.8 and also got a FC reading of 1.5! I then tested my RO water and the PH was yellow, indicating 6.9 or less (but the CL was 0). Does anyone know if an RO system can cause this much of a drop in PH?
    Intex Metal Frame 18'x9'x52" Oval Above Ground ~5000 gal. Hayward Sand Filter. Hayward 1.5 hp pump. Sungrabber 2x20 solar heating panel.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Need Some Help With Reading PH

    Yes, you can add more drops of the PH reagent to see if that makes it simpler to read the color. The PH test is usually easier to read in bright light. If you hold the test cell up to a clear Northern sky (indirect sunlight) or a sunlit white surface it is often easier to read.

    Yes, reverse osmosis can change the PH. Nominally, the PH should be 7.0 after an RO filter. However, RO also removes all of the PH buffers, so the PH can swing around quite easily.

    A CYA of 80 is manageable, but can be quite annoying if you have to fight algae. I would lower it if practical, but if you want to live with it you can.
    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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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Need Some Help With Reading PH


    That pH is a little difficult for many when you first get it. It gets almost second nature after a few tests. I always got my kids to give me their opinions when I first started testing and we would arrive at a consensus.

    PS - I should add that my kids are now teenagers and there is no consensus on any subject any longer!
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: Need Some Help With Reading PH

    I have the kids do the extra drops trick when they are testing when I'm out of town. I think you're on to the key to pH testing: Match the yellowness/purpleness to the samples.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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