Differences in Salt Level Readings

[Kit]

I have been monitoring the salt level in my spa on a daily basis as part of my data gathering to address another issue. I have been comparing the readout from the IntelliChlor SWG to the drop test results from the Taylor kit. As indicated below, there have been some significant deviations between the 2 results on certain days (e.g. on July 18). I have been diligent to take the readings during the same time of day, with the circulation pump on & obtaining the water sample (for the drop test) at a depth of about 18". Could someone offer some thoughts on the deviations? Thank you so much.

SALT LEVEL READINGS

DATE/ SWG READOUT/ TAYLOR KIT

July 5 3350 3200
July 6 3350 3000
July 7 3350 3000
July 8 3200 3300
July 9 3950 3200
July 10 3000 2800
July 11 3000 3000
July 12 3200 3200
July 13 3150 3000
July 14 3800 3200
July 17 3500 3000
July 18 3450 2400

 

[mas985]

The Taylor kit is good only to +- 200 ppm so those results are consistent except maybe for the last one but that could just be a test error.

As for the SWG, many have reported that the IntelliChlor does not compensate properly for water temperature change. If you measure the water temperature at the same time as the SWG salt measurement, you will probably see the salt level go up with water temp and visa versa.

 

[pooldv]

Yes, salt reading definitely varies with temp on the Intellichlor. We are on season 5 with ours and gave up long ago trying to hit a number. We are just looking for all green lights. The good news is that it will not give any errors when it thinks salt is between 2800 ppm and 4500 ppm. So, we have a big easy target to hit. Aside from that we love our IC40.

 

[Kit]

The Taylor kit is good only to +- 200 ppm so those results are consistent except maybe for the last one but that could just be a test error.

As for the SWG, many have reported that the IntelliChlor does not compensate properly for water temperature change. If you measure the water temperature at the same time as the SWG salt measurement, you will probably see the salt level go up with water temp and visa versa.

Mark: I feel confident that I eliminated the possibility of a test error with the Taylor kit on July 18. I repeated the test twice more & got the same reading. 'Tis perplexing.

Thanks for the suggestion to note the water temperature when I take the SWG reading. Will do.

 

[Kit]

Yes, salt reading definitely varies with temp on the Intellichlor. We are on season 5 with ours and gave up long ago trying to hit a number. We are just looking for all green lights. The good news is that it will not give any errors when it thinks salt is between 2800 ppm and 4500 ppm. So, we have a big easy target to hit. Aside from that we love our IC40.

I think that I am being a bit anal about targeting the salt level to a specific number. (I'm a new spa owner!). Since I try to monitor the TC daily & the FC weekly, problems associated with too little (or too much) chlorine shouldn't be an issue.

Also, after 4 months since the IntelliChlor was installed, I cleaned the cell. No visible deposits prior to cleaning; and no foaming when I poured in the acid/water mixture. So I feel confident that I am not getting any spurious SWG readings from a dirty cell sensor.

 

[bdavis466]

Avoid cleaning the cell if it doesn't need it. The coating on the blades in the cell is essential to the operation of the unit. Acid will eventually eat this coating and shorten the lifespan of the unit.

If you are on top of your water chemistry and monitor CSI ranges as recommended on this site, you should never need to clean your cell.

The actual salt level really isn't that important unless it is too low or too high for the cell to operate. This is a very wide range on most cells, Pentair included.

 

[mas985]

I think that I am being a bit anal about targeting the salt level to a specific number. (I'm a new spa owner!).

I would not disagree but as long as the SWG is happy and does not say the salt level is too high or too low, it really doesn't matter.

Mark: I feel confident that I eliminated the possibility of a test error with the Taylor kit on July 18. I repeated the test twice more & got the same reading. 'Tis perplexing.

It is impossible to eliminate error because it is built in to the test method. Each drop is 200 ppm and you don't know if the true salt level is between the last drop or the next drop. The only thing you have done is to make the test repeatable but accuracy and repeatability are two different things.

 

[Kit]

Avoid cleaning the cell if it doesn't need it. The coating on the blades in the cell is essential to the operation of the unit. Acid will eventually eat this coating and shorten the lifespan of the unit.

If you are on top of your water chemistry and monitor CSI ranges as recommended on this site, you should never need to clean your cell.

The actual salt level really isn't that important unless it is too low or too high for the cell to operate. This is a very wide range on most cells, Pentair included.

Thanks, Brian. As soon as I poured the acid mixture into the cell & saw that there was no foaming action, I immediately dumped the mixture & rinsed out the cell.

 

[Kit]

It is impossible to eliminate error because it is built in to the test method. Each drop is 200 ppm and you don't know if the true salt level is between the last drop or the next drop. The only thing you have done is to make the test repeatable but accuracy and repeatability are two different things.

I agree, Mark. But it still seems odd that the drop test had a discrepancy of 600ppm from the same test on the previous day & a 950ppm discrepancy from the SWG from the previous day. Nevertheless, I agree with the comment that if the salt level remains within the range that illuminates the green light, all is good with the world.