Pool Math results vs ORP requirements

H-12 1/2 Mike · Oct 3, 2020

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Ewald
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Build Type: Plaster
Volume: 16400 gallons
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Latest Test Result Summary:
FC: 6.2 (7 hours ago)
CC: 0.0 (7 hours ago)
pH: 7.7 (7 hours ago)
TA: 80 (yesterday)
CH: 240 (yesterday)
CYA: 90 (5 days ago)
SALT: 4760 (7 hours ago)
TEMPERATURE: 72° (7 hours ago)
CSI: -0.42 (7 hours ago)
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Above are my test results from this morning. I am awaiting a shipment of calcium increaser to raise my Ch to around 380-400 which should in turn help increase my CSI. The question is: Why is my ORP reading (portable device) only at 511 well out of the acceptable range of 680-720? My suggested Cl range is 4 - 12 according to Pool Math. It appears that the acceptable range should much higher in order for the sanitizer to be more efficient. Any suggestions??

mknauss · Oct 3, 2020

ORP is disrupted by CYA in the water. The forum has seen few ORP systems that consistently work and can be relied upon.

H-12 1/2 Mike · Oct 3, 2020

I do not have an ORP system just a measurement tool. The effectiveness of the chlorine is hindered by the high CYA value so that means a higher CL is needed to be effective. The ORP just measures the effectiveness of the CL. With my level of 511mv would not it take over 3 hours to kill any contaminants? Whereas at 700mv the kill rate is almost instaneous. My question was is the range of CL in Pool Math too low for the high CYA value of my pool?

mknauss · Oct 3, 2020

ORP data is not in my wheelhouse. Follow TFPC recommended levels.

Bvacchiano · Oct 3, 2020

Ignore ORP. Absolute useless measurement.

dschlic1 · Oct 5, 2020

I have found that CYA levels higher than 30 ppm cause ORP not to respond to changes in FC levels.

H-12 1/2 Mike · Oct 5, 2020

Thank you for the information. Now for the long process of lowering my CYA. What ORP readings do you get at 30?

Donldson · Oct 5, 2020

Lowering your CYA enough to get a reasonably reliable (though that's arguable) reading out of your ORP is going to cause your chlorine to burn off faster. That's going to require you to run your SWG longer to compensate.

Why is it that important to get an unnecessary ORP meter working that you're willing to sacrifice your SWG?