Salt Levels

[DONNIE]

My Taylor salt kit says my salt level is 3400ppm. I tested it 3 times over the weekend and always come up with 3400ppm. I added the salt Friday and it is completley dissolved and the pump has run 24/7. My PoolPilot Dig-220 says salt is @ 4500ppm. Am I missing a setting or adjustment?

Donnie

[chem geek]

The salt level reported by an SWG is usually just a calibrated measurement of conductivity, not an actual measurement of chloride level (measured as ppm salt) that your test kit measures. The conductivity of your water will vary based on temperature (higher conductivity at higher temperature) and the SWG might not be compensating for that in its display (though usually this problem is seen when the water is too cold and the SWG incorrectly reports a too low salt level). Also, the conductivity will vary based on other ions in the water such as those that come from TA and CYA levels or from sulfates in the water and the SWG may not be adjusting for that if such levels are different from whatever "standard" level that was expected.

Just out of curiosity, what kind of acid do you use -- Muriatic Acid or Sodium Bisulfate? Do you use any sort of non-chlorine shock (potassium monopersulfate)? You could have sulfates in your water that are providing more conductivity but are not measured in the chloride (salt) test kit, but the difference of 1100 ppm seems quite large.

Richard

[DONNIE]

I use muriatic acid and BBB right now. Though I have the salt in the pool the water is 48F so I have just been adding a little bleach to keep it right. Everything SEEMS fine. Water is crystal clear. Will the SWG pay any attention to that number and adjust output or will it go by my manual settings?

Donnie

[nater]

I also have a DIG-220. Right now my water temp is around 47, so the control panel has dropped cell output to 1%, and the salt reading is 300 ppm lower than my Taylor test kit results, which I trust. As Richard says, typically cold water will give you a lower reading than actual.

If you're just setting up your system, you may need to "calibrate" the cell. This is done by taking several measurements and then manually entering the value into the Control panel. See your manual or the Poolpilot web site for more detail.

I'd trust your manual test results for salt level for now. Keep the BBB method in place until you get closer to swimming temp. By then you can trust the Pool Pilot display to be closer to reality and do the calibration. Hopefully PoolSean will see this thread and add the expert opinion.

[Poolsean]

You all are too good and can just as well replace me. The feedback are all correct. The AutoPilot salt display is temperature compenstated so it should remain fairly consistent, and is based upon a true thermistor type temp reading. As Nater said, go through the MAINTENANCE menu to SALT CALIBRATION and adjust the display to your test results.

[DONNIE]

Thanks guys. I saw in the owners manual where it states "contact the factory for calibration solution". I'll try to adjust it this weekend through the maintainence menu.

Donnie

[Poolsean]

Calibration solution is really to verify that our testing method is accurate. The Taylor is probably the best readily available kit, but is a little TOO accurate for us salt people. We're just looking for continuity. Even if this is as a result of sulfates or TA or CYA, those usually don't add up enough to interfere with the salt reading.

Regarding Richards assumption with CYA and corrosion, there is evidence that even with indoor pools, CYA helps to prevent corrosion with as little as 15 ppm.

[chem geek]

Calibration solution is really to verify that our testing method is accurate. The Taylor is probably the best readily available kit, but is a little TOO accurate for us salt people. We're just looking for continuity. Even if this is as a result of sulfates or TA or CYA, those usually don't add up enough to interfere with the salt reading.

Regarding Richards assumption with CYA and corrosion, there is evidence that even with indoor pools, CYA helps to prevent corrosion with as little as 15 ppm.
Sean,

Really? That's very interesting news about corrosion and yet one more reason why CYA should be used (in small amounts) in indoor pools. It also helps slow down disinfection by-product (DPB) production and reduces degradation and fading of swimsuits (as my wife will attest to). Thanks for the additional information. When you get a chance, I'd like you to bring your perspective into The China Shop thread I created on the salt water corrosion issue. It sounds like there's going to be multiple "additive" sources involved and probably simple solutions that will require education (especially to pool builders).

Richard

[DONNIE]

Retested salt to verify ppm @3400 and recalibrated my PoolPilot. Everything is perfect now. Sean, reading all of your previous posts regarding the PoolPilot and the advice you have given me reassures me that I definitly made the right purchase. Thanks to you and all the others who have helped me. I have a firm grasp on water chemistry and I also have a sparkling crystal clear pool!

Donnie