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Thread: AutoPilot pH control calibration

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    AutoPilot pH control calibration

    Last spring I installed an Autopilot with the chemistry control... wow, talk about making things easy. I love it. I just opened things up again this year to find the display reading a pH of 9.5, my pool supply store (machine read strips) telling me that my pH was low at 6.4, and my test kit telling me that it was 7.6. I'm going to assume that the test kit is the one to believe. I am wondering if it is normal for the AutoPilot to be so far out of calibration. I didnt expect it to be so far off. Last season, it came out of the box showing the same number my drops were telling me. What happened while it was sitting in the basement for the past 6 months? Should I be looking for a problem somewhere else?

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    JasonLion's Avatar
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    May 2007
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    Welcome to TFP!

    There are quite a few possibilities. The connection of the probe to the chemistry controller might not be fully seated and locked. You might have accidentally stored it dry over the winter. The probe might be dirty, clean as described in the manual. The probe could be more than two years old. You might have added bleach or borax or soda ash directly to the skimmer. You might not have waited long enough, give it a day with the pump running after installing before believing the numbers.
    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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    Guest
    pH probes need to be stored wet. If you allow them to dry out they are basically ruined and need to be replaced.
    They also need to be calibrated on a regular basis with standard solutions.
    Also, they do wear out and need to be replaced.

  4. Back To Top    #4
    Alright... so I'm guessing the answer to my question is that the numbers are further off than might be expected. I did store the probe wet per the instructions but have not cleaned it. I'll give that a try. Of course waiting a day is pretty easy to do too.

    Thanks for the welcome. This is a really friendly and helpful place. I've been lurking for some time but have been able to find answers to all my questions without even posting!

    Quote Originally Posted by JasonLion
    Welcome to TFP!

    There are quite a few possibilities. The connection of the probe to the chemistry controller might not be fully seated and locked. You might have accidentally stored it dry over the winter. The probe might be dirty, clean as described in the manual. The probe could be more than two years old. You might have added bleach or borax or soda ash directly to the skimmer. You might not have waited long enough, give it a day with the pump running after installing before believing the numbers.

  5. Back To Top    #5
    When I had my TC system installed new, it had similar readings that were way out of line with the actual pH. I spent countless hours trying to troubleshoot the thing, because on occasion it would work for a few hours at a time. In the end, it was a faulty pH probe and all issues were solved with replacement. To save you trouble and time, I would recommend changing the probe if it does not show proper behavior after cleaning within 48 hrs.

    Also, be sure to replace with a probe that is compatible. I tried to use a Sensorex pH probe - it wouldn't work. Safest bet is to go with a CAT pH probe. CAT is the OEM for the pH probe that comes with the TC system.
    17,500g, IG pool/spa, pebblesheen, Autopilot TC SWG, Pentair 4x160 variable speed pump. Sta-rite cartridge filter, Sta-rite Gas heater, Polaris 280 cleaner

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