Which salt level is correct?

[SFM]

Hi all, we are about 10 months into our 1st pool. I am trying to figure out which salt level result to trust more. Table below shows results from the TFT salt test (chromium/silver nitrate) and the SWG reading (pentair intellichlor-40) using the reading taken at same time as water sample for each test (and each sample collected from 2-3 areas ~18” down). Overall looks like the SWG underestimates levels by 150-800 compared to the TFT.
Which result do I go by?? TYIA!
TFT. SWG
4400 3600
3800 3300
3600 3150
3200 3050
3800 3300
3400 3000
3000 2650

 

[JamesW]

They are close enough.

I would be more concerned about why the salinity is going down so much.

 

[JamesW]

The Pentair Intellichlor IC-40 has a known problem with the temperature sensor, which can throw off the salinity reading.

You can test the temperature reading.

 

[SFM]

That’s very helpful thanks JamesW.
I should have mentioned that those readings were over the course of several months and in retrospect would’ve been helpful to put down dates, water temperature and when salt was added. To be honest I’ve been letting the salt readings drift down as I was worried about over-sallting and having issues from that, but it sounds like I can relax and not worry about being too precise.
Thanks again!

 

[Jimrahbe]

SFM,

I never trust the salt readings from the cell.. It is more like a good guess, than an actual measurement.

Also it is pretty easy to read high when using the Taylor style salt test kit. You really need to use a speed-stir or smart-stir when testing. Unlike a lot of drop tests, you stop counting the moment the change happens, you don't keep adding drops as the color changes.

As you are testing you will notice that a drop will make the color change from milky to copper color and then it will quickly change back to milky. The first drop that changes the color and it stays that way is when you stop. If you add more drops, it will make the color darker, but that is not what you are looking for.

The main problem is that it does not matter what the "actual" salt level is, it only matters what the cell "thinks" the salt level is. You have to make the cell happy for it to work. As long as I can keep the actual salt level below 4000, and still make the cell happy I am good. If I have to go above 4000, it usually means the thermistor inside the flow switch is bad.

Thanks,

Jim R.