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Thread: Low ORP? : High FC - pH Constant - Zero CC

  1. Back To Top    #1

    Join Date
    Jun 2015
    Location
    Phoenix, AZ
    Posts
    216

    Low ORP? : High FC - pH Constant - Zero CC

    It's been around two weeks since we filled our new pool and I am constantly checking it to understand its temperament.

    For the last couple of days, the ORP reading has been around 540 to 620 - never reaches 650.
    The Chlorinator automatically gets turned on by the Hayward control system if the ORP is below 650. So, I am seeing constant chlorination for the last couple of days or so.
    FWIW - all equipments are new - the probes are only a couple of weeks old..

    My current readings are:
    FC - 11
    CC - 0
    TC - 11

    pH - 7.5
    TA - 100
    CH - 300
    CYA - 55

    During the last week, my ORP values were almost always around 700+... even if the ORP reading came below 650, it would go up to 700+ within an hour or so.

    But, during this week, the ORP is not moving above 620.
    All this time, pH was a constant 7.5 - checked very often with TF-100

    I also checked every few hours last night 7 pm to 5 am - the ORP never went beyond 620~~ and the chlorinator was constantly running.

    Should I turn off the chlorinator and do an OCLT this weekend?
    2015 build (link)| 16.5 K gal | Salt Water | IG rect | 35'x16' | 568 sf | 105 ft peri | depth 3'-5' | PV3 in-floor | 2 Venturi skimmers | MDX+SDX drains | T-CELL-15 SWG | Hayward Ecostar VS pump | Hayward 7220 DE Filter | Aqua Cal Icebreaker Heat / Cool pump SQ166 | Hayward Sense & Dispense PH Controller| Omnilogic | Pebble Sheen Blue Surf | Ultra UV | Stenner acid pump | Coverstar Automatic | TF-100

  2. Back To Top    #2

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Low ORP? : High FC - pH Constant - Zero CC

    Why do you believe that the ORP reading means anything? ORP is known to be unreliable in an absolute sense. Most ORP sensors do not do well at higher CYA levels. The CYA fouls the sensors. Also, ORP gets interference from many different factors.

    With a properly working Chemtrol sensor, the ORP with your FC and CYA and pH (at 85F) would be around 712 mV and with an Oakton sensor it would be around 676 mV so your low numbers are unusual. It most likely does NOT mean you need to SLAM but rather that your sensor is not reporting properly. This is why we normally do not recommend ORP sensors. Commercial/public pools are required to test with manual test kits several times per day and any ORP system is only used for process control where the setpoint is set by the manual test kit readings.

    Note that the Hayward Sense and Dispense manual says the following about ORP sensors:

    Probe Maintenance
    The probes must be clean and free from oil, chemical deposits and contamination to function properly. After saturation in pool or spa water, the probes may need to be cleaned on a weekly or monthly basis depending on bather load and other pool specific characteristics. Slow response, increased need to calibrate pH, and inconsis- tent readings are indications that the probes are in need of cleaning.

    To clean the ORP and pH probes, run the Clean Probe Wizard within the Settings Menu on the Aqua Rite Pro or the Maintenance Menu on the Pro Logic. This Wizard will walk the user through the probe cleaning process. Answer the questions when prompted, and follow the instructions for proper cleaning.

    To clean the probes without running the Wizard, turn off input power to the Aqua Rite Pro or Pro Logic. Disconnect the probe connectors from the communication box, unscrew the probe and carefully remove them from the Probe Cell. Clean the reference junction (the white ring at the bottom of the probe body) with a soft toothbrush and regular tooth paste. A household liquid dishwashing detergent may also be used to remove any oil. Rinse with fresh water, replace teflon tape on threads and reinstall probes. If properly cleaned probes continue to provide unstable readings or require excessive calibration, the probes should be replaced.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  3. Back To Top    #3

    Join Date
    Jun 2015
    Location
    Phoenix, AZ
    Posts
    216

    Re: Low ORP? : High FC - pH Constant - Zero CC

    Thank you, @chem_geek ...

    Last night, I performed the OCLT turned off chlorinator at 4 pm..

    7:30 pm FC = 11
    6:00 am FC = 10.5.
    So, there is really no organic matter.. its my OCD that's the problem

    Also noticed that the ORP reading went back to 'normal' reporting around 700ish at night.

    Thanks for the Sense and Dispense quote...I really must go back to reading the manuals back to back.. missed the fact that I may need to clean the probes regularly. Scheduling this for my monthly maintenance tasks.
    2015 build (link)| 16.5 K gal | Salt Water | IG rect | 35'x16' | 568 sf | 105 ft peri | depth 3'-5' | PV3 in-floor | 2 Venturi skimmers | MDX+SDX drains | T-CELL-15 SWG | Hayward Ecostar VS pump | Hayward 7220 DE Filter | Aqua Cal Icebreaker Heat / Cool pump SQ166 | Hayward Sense & Dispense PH Controller| Omnilogic | Pebble Sheen Blue Surf | Ultra UV | Stenner acid pump | Coverstar Automatic | TF-100

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