Cartridge for Watkins( HotSprings/Caldera ) Freshwater Salt System went bad after 5 weeks

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Roaddogmm

Active member
May 26, 2020
25
Cary, NC
I'm curious, have any of the folks with the Freshwater Salt System by Watkins had a cartridge go out early? My tub is only 6 weeks old, and after about 5 weeks, I started getting inactive/low status for my SWG on the tub. I checked all the recommended things( salt level, clean/degrease filter, soak cartridge in ph down to descale, etc ) with no luck. Finally, after talking with my dealer and finding out they are out 2 weeks on service calls, decide to just go ahead and buy the replacement cartridge so I can swap it out and test. Sure enough, put in the new cartridge and everything seems fine.

I'm curious, has anyone had a similar problem with this system?

I do plan to have them go ahead and come out on a service call( free first 6 months ) and see if they can explain why it seems the cartridge went bad quickly.

Thanks!
 
I keep it pretty much on the specs recommended, 7.4 PH, 50 calcium hardness, and around 60 TA. CYA is around 30, used the dichol/bleach method when initially starting the system. Testing all these with a taylor test kit.

The failure caused the system to read the salt as being too low, and was shutting it off. I had the watkins salt test strips that seemed to indicate salt was fine, and ordered some more from aquachek( which are way better ), and they showed salt was fine too. Replacing the cartridge and the system shows salt readings pretty much exactly like the strips and its producing chlorine as expected.
 
I have never seen one of these, but I have heard that they have some issues. I also heard about the low calcium they recommend, though I don't recall the exact numbers. Seems to be pretty corrosive water, with such a low saturation index. I have not been able to discover why they have issues or why they recommend such low readings. Would you refresh my memory on their recommendations?
That said, I would raise calcium to the upper end of the recommended range (say 100-125 iirc) and alkalinity closer to 90 and ph around 7.6 to avoid other damage to equipment and plumbing from corrosive water. I couldn't say if corrosive water is the cause of your issue, but I suspect it plays a part. I also couldn't say if balanced water is good for the cartridge, but it's good for everything else in the spa.
@JoyfulNoise , you are a chemical guru and a fan of salt systems as I recall. Any thoughts?
 
RDspaguy said:
I have never seen one of these, but I have heard that they have some issues. I also heard about the low calcium they recommend, though I don't recall the exact numbers. Seems to be pretty corrosive water, with such a low saturation index. I have not been able to discover why they have issues or why they recommend such low readings. Would you refresh my memory on their recommendations?
That said, I would raise calcium to the upper end of the recommended range (say 100-125 iirc) and alkalinity closer to 90 and ph around 7.6 to avoid other damage to equipment and plumbing from corrosive water. I couldn't say if corrosive water is the cause of your issue, but I suspect it plays a part. I also couldn't say if balanced water is good for the cartridge, but it's good for everything else in the spa.
@JoyfulNoise , you are a chemical guru and a fan of salt systems as I recall. Any thoughts?
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Here is straight out of the manual. 75 is the top end of the calcium hardness, they actually recommend you soften it down if you are above that.
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So I looked a bit at the Watkins system and the online user and setup manual. The "cartridges" are just the standard MMO titanium electrodes of an SWG cell packed in an easy to replace carrier. They user manual is quite clear that these are considered consumable components and that they will last, at most, 4 months. I'm going to go out on a limb here and say that the electronics driving these electrode cartridges is probably fairly unsophisticated and so it just uses a constant DC current to drive them with no current reversal built into the system. Generally speaking, unless these electrodes are properly designed and run at correct voltage and currents, they can easily get coated up with calcium scale or the coating can essentially get dissolved away. Most high-end, pool grade SWG's have very sophisticated power supplies and do periodic current reversal to ensure that the anodes all wear out the same way. I'm pretty sure that these hot tub systems are a lot less sophisticated and just expect the user to throw away electrodes whenever they are not working.

The low saturation index is probably to avoid calcium scaling inside the SWG cell. Because the pH of the water flowing through the chlorine generator can be very high locally inside the unit, you need very soft water to avoid scaling up the electrodes and prematurely killing them. As far as the health of the rest of the tub goes, metallic corrosion is not really related to the saturation index and it is driven more by low pH conditions and the presence of other ions that enhance certain types of corrosion. The heating element is the most susceptible to corrosion and so if the tub is going to be operated at low saturation, the heater should be titanium metal, not steel or Incoloy. The body of the tub is typically acrylic and most of the plumbing is going to be be either PVC or PEx tubing so low saturation won't really affect those. Again, the main driver of corrosion is low pH so if you maintain such a low TA and CH, keep a careful eye on pH.

Adding 50ppm borates to the tub will help to act as a good pH buffer and will help to keep the pH inside the chlorine cell lower. So you might find that helps with cartridge longevity.
 
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RDspaguy said:
Thanks @JoyfulNoise that's good information to have. Would low SI affect rubber gaskets, o-rings, pillows, and such, or is that more ph as well?
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Saturation doesn't matter as much for those and the pH has to be very extreme (either high or low). What matters most for polymer materials like plastics and rubber is basically the amount of oxidizer present and the fact that the tub is full of water. Water is the greatest solvent and can react with and dissolve many things. Organic materials like polymers, plastics and rubber undergo hydrolysis reactions which tend to destroy the chemical bonds that makes them hardened against chemical and physical wear. Rubber is great example of this because before vulcanization was discovered (essentially cross-linking reactions using sulfur), natural gum rubber materials would completely degrade upon exposure to water. They still do degrade from water but cross-linking makes that process much slower. Oxidizers like chlorine speed up those reactions too. pH can play a role but it's minor. Rubber o-rings and seals are just consumable items and always subject to wear and tear; they need a regular schedule of inspection and/or replacement; water of any kind really kills rubber materials.

So in reality, keeping tight control over chemistry is what makes things last longer. Tubs and pools are always subject to user laziness and lack of attention and so that leads to lots of work for the service guys.
 
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Thanks for the reply, it makes sense. I added 50ppm of borates early on, and find pH to be pretty stable. I keep it at 7.4, and it seems to creep up to around 7.6 once a week, then I'll add a dose of muriatic acid to correct.

I did read something in a manual, may have been the dealer troubleshooting version I found online, that talked about the system reversing polarity. I also found the info in there about a acid dip to clear out calcium buildup, which I tried. I'm not sure I was supposed to see that manual, but someone let Google index it 🤣🤣

The issue I was seeing was the system reporting salt as low, when it was ok. The system shots itself off in that condition. Upon changing the cell it is reporting fine immediately. For a couple of weeks now it's been great, and the chlorine output actually seems much better to the point I've not supplemented liquid chlorine at all, and have turned the level down a bit.

My local dealer refused to replace the cell, I figured they would throw me a bone on a 1 month old tub, but no dice. I reached out directly to Caldera though through social media, and they immediately agreed to send me a replacement cell, so I'm happy with that. We'll see how the lifetime is on this one, I'm hopeful.
 
Usually a “low salt” reading from an SWG cell is a consequence of calcium build up on the plates. The calcium build up effectively reduces the conductive area of the plate making the circuit look like it has higher resistance which appears similar to low salinity. The “salinity” reading from these units is nothing more than a conductivity measurement so they are a glorified TDS meter (and a pretty bad one at that). Do not use a strong mineral acid to clean the plates. Cleaning vinegar (6% acetic acid) will work fine. Cleaning the plates will sometimes restore their ability to produce chlorine if the mixed metal oxide coating isn’t damaged.
 
JoyfulNoise said:
Usually a “low salt” reading from an SWG cell is a consequence of calcium build up on the plates. The calcium build up effectively reduces the conductive area of the plate making the circuit look like it has higher resistance which appears similar to low salinity. The “salinity” reading from these units is nothing more than a conductivity measurement so they are a glorified TDS meter (and a pretty bad one at that). Do not use a strong mineral acid to clean the plates. Cleaning vinegar (6% acetic acid) will work fine. Cleaning the plates will sometimes restore their ability to produce chlorine if the mixed metal oxide coating isn’t damaged.
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Thanks, I had cleaned them once with ph down as suggested in the dealer manual. I saw some mentions of vinegar but wasn't sure if i should dilute it or not.

I'm crossing my fingers the current cell lasts at least the promised 4 months, it seems from the little info i can find on this that it is not a common issue with this system.
 
Roaddogmm said:
Thanks, I had cleaned them once with ph down as suggested in the dealer manual. I saw some mentions of vinegar but wasn't sure if i should dilute it or not.

I'm crossing my fingers the current cell lasts at least the promised 4 months, it seems from the little info i can find on this that it is not a common issue with this system.
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If “pH down” is granular sodium bisulfate, you definitely don’t want to use that. Bisulfates will destroy the MMO catalyst coating. If by chance you a referring to muriatic acid, that’s only advisable to use if it is heavily diluted (10:1 ratio or more). Vinegar is best because the pH isn’t too low and the acetate ion doesn’t damage the MMO layer.

Good luck with the new cartridge. Hope it lasts and keep us posted on it.
 
JoyfulNoise said:
If “pH down” is granular sodium bisulfate, you definitely don’t want to use that. Bisulfates will destroy the MMO catalyst coating. If by chance you a referring to muriatic acid, that’s only advisable to use if it is heavily diluted (10:1 ratio or more). Vinegar is best because the pH isn’t too low and the acetate ion doesn’t damage the MMO layer.

Good luck with the new cartridge. Hope it lasts and keep us posted on it.
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Interesting, I did use graular sodiium bisulfate. Maybe the phDown had did the cell in when I cleaned it, I think it did get worse after that. I was following some instructions I found in the dealer FAQ for the system.


It says I generally shouldn't need to do this during the usable life of the product( 4 months ), but if I ever deem it necessary i'll definitely go vinegar or heavily diluted muriatic acid in the future.

Thanks for all the info!
 
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