Salt cell reading high but salt is really low

[Wenz]

I need some help troubleshooting my salt cell. The salt level of my pool is around 2100 (tested using strips), but my salt cell (Hayward T-Cell-15) is reporting 3400. Below are my water test results and what the AquaRite LCD is reporting.

In ground pool, ~11,000 gallons
CYA ~60
TA ~100
Total Calcium ~1800 (I know this is really high, but I do not want to drain the pool at this time; probably a topic for another post)
pH ~7.6
Cl ~4
Salt ~2100 (I tested and the pool store tested it using strips. I am ordering a K-1766 test kit.)

AquaRite
Hayward T-Cell-15 (it is about three years old)
100P
-3400
AL-4
r1.33
3400
79
25.2
6.57

The cell is producing Cl; it is holding the Cl level around 4 at 100% running about four hours a day. Though, I think this amount of Cl is lower than it would be if the salt level were in the proper range. The cell looks pretty clean; I acid washed this month. I do not want to add more salt for fear of causing the salt cell to report a high salt warning and stop working.

I spent a lot of time searching through the forums, but I could not find another thread with this exact problem. Normally, if the cell is going bad, the cell would think the salt level is lower, not higher. I also saw people getting really strange readings when the AquaRite board is fried, but these readings are very consistent. It has always been reading high (500-700 ppm), but not like the 1300 ppm it is currently.

I was wondering if:

1. Is it possible that the high total calcium level is causing the cell think the salt level is higher? My understanding is that the cell is looking at the resistance in the water, so all those dissolved solids could be affecting the reading.
2. Could bad circuit board be causing this?
3. Could a bad cell?

I appreciate any help.

 

[JamesW]

3,400 is the actual salinity. The strips are wrong.

How are you getting 1,800 for "total calcium"?

Are you measuring "Total Hardness" or calcium hardness?

 

[Wenz]

Thank you for the quick reply.

I tested the "Calcium Hardness" using a TF-100 test kit.

 

[JamesW]

You should be able to confirm that the actual salinity is about 3,400 ppm when you get the K-1766 salt test kit.

I suspect that the calcium hardness result might be an error.

Are you getting a good transition for the endpoint color change?

 

[Wenz]

You should be able to confirm that the actual salinity is about 3,400 ppm when you get the K-1766 salt test kit.

I suspect that the calcium hardness result might be an error.

Are you getting a good transition for the endpoint color change?

I will retest the calcium hardness using that alternative method. I did not get a clean transition. I have never added anything with copper to the pool, but I possibly could have some.

 

[Wenz]

One data point I did not mention in the original posting, is that when I put the salt cell back in last month (I take it out for the winter), the AquaRite would not generate. The Check Salt light was on (I cannot remember if it was flashing or on steady). I added a bag of salt to the pool, which should increase the ppm by about 400. After adding the salt, the Check Salt light turned off and the salt cell has been making Cl. If the current 3400 reading is the true salinity, then I would think that the cell would have worked before adding salt. Is that reasoning correct?

 

[JamesW]

You can't go by the initial salinity reading.

You have to wait for the water to mix and for the average salinity to catch up.

 

[Wenz]

I received my K-1766 salt test kit. I have tested it twice and got around 2800 both times. My cell is reading around 3300, so it is still around 500 ppm higher. So back to my original questions, plus more:

1. Should I be assuming the K-1766's 2800 ppm value in the most accurate measurement (versus the strips or cell)? The 2800 number seems reasonable since the cell was not operating until I added the sack of salt to increase the ppm by about 400 ppm. If so, then:
2. Is it possible that the high calcium hardness level is causing the cell to think the salt level is higher? My understanding is that the cell is looking at the resistance in the water, so all those dissolved solids could be affecting the reading. Note, I did try to re-test the total hardness twice following the video posted above and never got a hard transition, so not sure what the real hardness is.
3. Could bad circuit board be causing this?
4. Could a bad cell?

I appreciate any more help.

 

[JamesW]

Deleted.

 

[JamesW]

The SWG is fine and the salinity reading is close enough.

Just go by the cell reading.

The calcium has no effect on the Aquarite salinity reading.