Hot Tub salt level shows too high but test strip is perfect.

[jtedescojam]

HotSprings hot tub doesn't register the salt level properly. It will show it's too high OR too low. i can't get it in the middle.

Steps I took:

1. Checked the water with the test strips and the water was too high
2. Tested to make sure strips weren't expired and tested on tap water and the strips work, verified the level was too high
3. emptied the tub 75% and refilled
4. test strip showed too low.
5. Added a cup of spa salt at a time until the test strip was perfect.
6. Salt cell is operational and tests too high

Someone mentioned that the salt sensor can be off.. is that true? how do I get this to read properly? if the salt cell cannot verify the salt level, the tub won't produce chlorine and might as well not be working. Please help save me $300+ just to have a guy come out and look at it. He'll probably make me buy a new cell. That's another $800... help!

 

[Mdragger88]

Is this the freshwater system? If so, how old is the cell cartridge? If not - what system is it?

 

[JamesW]

Taylor K-1766 Salt Test Kit

tftestkits.net

 

[jtedescojam]

Is this the freshwater system? If so, how old is the cell cartridge? If not - what system is it?

FreshWater® Salt System Ready. the cell cartridge is 3 years old and is operating fine. cleaned as well.

 

[Mdragger88]

To clarify,
The Freshwater cell cartridges are disposable & generally only last 4-6 months at best. A replacement 3 pack costs around $300.
The older ACE salt system has a longer lasting cell that usually lasts about 3 years & costs about $800 although there are generic aftermarket replacements available on Amazon that are in the $200-$300 range.
As far as I can tell both types of systems “assume” the salinity level by measuring current through the cell. There’s no separate salinity sensor. If the cell’s coating is deteriorated (as happens over the life of all swg cells) or if there is scale present that will effect the measurement. You can try gently cleaning it with vinegar.
The rare earth coating on the cell (which is what produces fc) is removed some everytime the cell is cleaned & as it gets used until eventually there’s no coating left & the cell stops producing. Low salt warnings with no scale present are generally a sign of a dying cell. Many people who just “feed” the cell salt without testing often end up with high salinity.


To further complicate matters, The test strips (if just opened) can be off by +- 500 ppm - they get more unreliable the longer they have been opened.
the kit James posted is +- 200 ppm & remains that way for the shelf life of the reagents if stored properly.
Also, aside from the accuracy of the strips, if you added salt then immediately tested the water it’s quite possible that it was not fully dissolved/dispersed in the water so you further convoluted your results thus putting in more salt than necessary.
It is recommended to not re-test salinity or turn on a swg cell for 24hrs after salt has been added to a pool, I tend to wait 6-12 hours in my small spa.
Failing to wait risks a high concentration of salt going through the cell & frying it (for lack of a better term).
For now I suspect you should replace a little water at a time until the swg is happy. If that doesn’t work then it may be time to replace the cell.

 

[jtedescojam]

Yes I was afraid of that. I have an ACE salt system that has the $800 cell. You're right in that I was adding salt and running the tests almost simultaneously but also running the jets for about a half hour and then testing again. repeating the process until the SWG was happy but it stayed at 'low' until the strips were showing me the right level, then I closed it up and waited a day... the next day the line jumped high. When the cell was brand new, it worked flawlessly within only a few minutes of adding salt so that's what I kept doing... but it sounds like the cell is deteriorating. Do you think I should try this process again?

Let out 25% of the water, refill, wait 24 hours and test. Add one cup of salt, wait 24 hours and test... and so on? or do you think it's officially shot? can I test the cell in a bucket of water or something?

I can't buy the cheap cell because the cell has a hard line direct into one of the filter caps and requires the entire hookup. $847.

 

[Mdragger88]

I would just replace a small amount of water at a time & see if that makes the cell happy. (No high salt alarm) no need to dump large amounts & then try to add back salt. That’s a yo yo game.

If the cell is dead/dying & the aftermarket one is not feasible you could just turn the system to zero/off when it’s breathed it’s last breath & get a drape over like the saltron mini. The cells for them last me around 18 months. The replacement cells are $149 ($99 before covid).

The dealer may be able to test the cell but you’re really at the expected end of life & they can’t be repaired. If you get a replacement & have crazy things still happening you may have a controller problem but what you described sounds like a failing cell followed by overshooting the salt addition.

 

[jtedescojam]

Thank you so much for working with me today. I will try to balance this and give it the time it needs. If I cannot balance it I will purchase a new cell and install it. This is a hotspring Grandee and quite expensive so I want to make sure this tub is running 100% perfectly. Calling the service tech will cost me $325 JUST to come out and look at it so I'm trying to save on that.

I also accidentally overflowed the tub and now one of my lights flickers. I'll attack that next.

 

[Mdragger88]

I can’t stress enough how important the salt test kit is (along with a k2006 or tf100)
I used to have a smaller intex pool with a very sensitive swg & relied upon the salt strips - it was always a battle. The local pool store used a meter but those can be off by 500 +- even if properly calibrated. I was always trying to average my results between the two & dealing with the yo yo. In a small body of water with a sensitive swg being off by an extra 300ppm matters. I also suggest that you weigh your salt & use PoolMath along with creeping up on your target.

 

[Methuselah]

I can’t stress enough how important the salt test kit is (along with a k2006 or tf100)
I used to have a smaller intex pool with a very sensitive swg & relied upon the salt strips - it was always a battle. The local pool store used a meter but those can be off by 500 +- even if properly calibrated. I was always trying to average my results between the two & dealing with the yo yo. In a small body of water with a sensitive swg being off by an extra 300ppm matters. I also suggest that you weigh your salt & use PoolMath along with creeping up on your target.

It SEEMS like salt level is in a range so the cell can operate within a prescribed current range? Makes me wonder if you can't check cell current?

I found this:
YouTube Vid on Salt Generator Cell

No idea if this helps, but I did note there were very few vids on YouTube for my search term "testing a salt chlorinator cell", so maybe manufacturers would rather sell you new ones instead of telling you how to test them? Sorry if it seems like I'm bashing the manufacturers, I'm sure testing involves liability and of course none of this means I have any idea about what I'm talking about since what I'm suggesting could be hard to do safely... (just wondering out loud I reckon).