Hayward SWG: instant salt vs average salt vs drop test results

Below are responses from Hayward to my questions concerning differences in salt readings displayed on the Omnilogic display vs. the Taylor K-1766 test kit:

The cell has 2 polarities. It reverses polarity based on the output percentage. The calibration procedure manually does this. When the polarity is reversed, the average salt resets. We don't assume either reading is correct. That's why you need to have it independently verified. Yes, we allow a variance of 500 ppm with our salt chlorinators.

The salt level is calculated by an algorithm in the main board that uses the voltage, amperage and water temperature. The unit may need to be calibrated. Go to the main MSP panel. Press on the chlorinator icon. Press on the magnifying glass icon. Press the +/- icon to calibrate the salt level.

The salt cell you have is an extended life cell. To make these cells extended life the cell plates are over coated with ruthenium, and this will make it read a higher salt level then you have in the pool. As the rethenium wears off the plates the salt levels will come down closer to what you have in the pool.

When using a variable speed pump it is recommended that the cell be plumbed in vertical position. By doing this the cell will fill even when the pump is running in a lower speed. If the cell is plumbed horizontally, and the pump is running in low speed, the cell will not fill completely with water, and cause it to read a false low reading.

Drain a few units from the pool and replenish with fresh water. The coating material is not visibly evident like debris would be. You want to have enough flow to completely cover the internal cell plates. Attempting to operate the unit on a low RPM setting will cause the plates not to be submerged and will give you erratic salt readings.

2800 ppm - that should cover all the cell plates if there's not a blockage to the water flow (like a clogged filter).

The variance is more than 500 ppm. Is the cell new? Some cells leave the factory with an extra coating on the internal cell plates. This causes it to read higher upon installation (usually around 1000 ppm higher). You can remove a few inches of water and replenish with fresh to "trick" the system. As the extra coat wears away, you should start to see the levels normalize. The extra coating will actually extend the life of the cell.

Hayward Case Management Specialist.

Oh the horror!

Just to add - I've had my pool for almost two years and have never used acid to clean my T15 cell. I use a long popsicle stick and hose. It stays fairly clean so far. From day one, my Omnilogic salt readings have not matched the Taylor salt test - they are always higher. They are however consistent. I use the Taylor salt test to determine when I need to add salt. I also use the Taylor K-2006C kit to test chlorine (and other chemicals) which always shows the cell is working fine. I am no longer going to worry about the reading on the panel - especially after the response I received from hayward.

From Hayward:

The unit resets the average salt level using the instant salt. That is how it calibrates. We allow for a variance of 500 ppm between the reading on the unit and the actual salt level. I recommend having the metal content of the water checked. Metals can cause a false high salt reading.

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During the winter I run pump at 1725 rpm (medium) for 1 hour and then 1035 rpm (low) for 7 hours and that keeps chlorine and debris under control. The chlorinator is set at 15% - 20% maximum. During the swimming season I crank up the chlorinator to 25% - 30% maximum. We do have a rubber duck that has a single chlorine puck that helps with chlorine and CYA. I set pump run time to meet my chlorine specifications and for debris cleanup. I do not believe in turnover rates. Run time will vary more during heavy use and windy conditions. I have mounted my salt cell in the "inverted" position to accommodate flow rate at low rpm level - so far so good. Because my pool is pebble, I have to maintain their chemical specifications to satisfy warranty.

Notice that PebbleTec uses the TDS (total dissolved solids) metric (aka salt) which measures all dissolved minerals, salts, metals, chlorides, and many other contaminants in the pool. TDS impacts water conductivity which is what I think the Omnilogic panel is actually displaying - TDS, not pure salt. If I understand correctly, if your pool water does NOT contain excessive metals, minerals, etc., then salt will be the primary component of TDS. The question for me now is - what is the best way to determine TDS if the Omnilogic is not accurate as stated by Hayward. It seems to me that you need to know both salt and TDS. Salt for sanitation and TDS for pebble finish - am I wrong here?

From PebbleTec if using salt cell:
ACCEPTABLE ONGOING MAINTENANCE RANGE* - AFTER 28 DAYS PPM = Parts Per Million pH 7.2 – 7.6 Total Alkalinity 80 – 120 PPM Calcium Hardness 150 – 250 PPM Total Dissolved Solids 2900 – 3900 PPM Chlorine 1 – 3 PPM CYA, Cyanuric Acid (Stabilizer/Conditioner) 30 – 80 PPM Langelier Saturation Index Range Between -0.3 and 0.3 * PTI Recommended Acceptable Range is designed for high-performance finishes and not recommended for traditional pool plaster.