Question about CL levels and salt cell lifespan...

Due to the high cost of salt cells for my Aqua Rite (T-15 cell) SWCG, I'm always looking for ways to maximize the cell's lifespan.

I keep my CYA level between 60 - 80 per manufacturer's instructions. At this level the Best Guess Chart recommends CL between 5 - 10, although I've read 5% of CYA is appropriate if using a SWCG (4ppm at 80 CYA).


Am I correct that the time my cell has to run to maintain CL at a particular level is a function of CL demand and not the absolute CL level? In other words, the cell wouldn't have to run any longer to maintain a CL level of 5 than it would a level of 8, since its just replacing the CL that has been used up?

The reason I ask is because I'd like to keep my CL level a bit higher than the minimum recommended to have some wiggle room just in case something goes wrong, such as the cell dying/malfunctioning. This would give me a chance to fix the issue before an algae bloom starts. However, if this is going to shorten the life of the cell, I may reconsider this strategy.

Jim, as I'm new to SWCG myself, I think the answer is: test your water daily for FC and pH so it doesn't get ahead of you. The SWCG provides a far more constant level of chlorine so lower, safe levels with a higher CYA works.

Quote:

---

Originally Posted by CarlD

Jim, as I'm new to SWCG myself, I think the answer is: test your water daily for FC and pH so it doesn't get ahead of you. The SWCG provides a far more constant level of chlorine so lower, safe levels with a higher CYA works.

---

Thanks for the feedback, Carl. :)

Early in the season I do test everyday. Once everything stabilizes, I test every other day, with the exception of when I go on vacation.


I'd still like to know if I'm on the right track saying that the running time for the cell depends on CL demand (loss) rather than the particular CL level you wish to maintain (4, 5, 8, etc).

I believe that at a given CYA, a higher concentration of FC will will lose more chlorine to sunlight. I don't know about SWCG cells - perhaps it's not total chlorine produced that limits them but some other factors. I know that the advice generally given here is to install a larger than recommended cell for extended cell life. I just don't know if there's a linear relationship between chlorine produced and cell life.

The % setting of the cell will depend on chlorine loss because that is the chlorine you are replacing every day.

Also, SWG cells are usually rated in amp-hours. So it is both the time the cell is on and the current running through the cells. Higher salt levels creates more chlorine but also higher amps (Goldline cells) and it is somewhat linear so that should be a wash because the higher chlorine levels means a reduced run-time (%).

Cell life seems to also be dependent on the chemistry balance. This is why some SWG owners experience very short cell life while others are much longer.

Quote:

---

Originally Posted by BigDave

I believe that at a given CYA, a higher concentration of FC will will lose more chlorine to sunlight. I don't know about SWCG cells - perhaps it's not total chlorine produced that limits them but some other factors. I know that the advice generally given here is to install a larger than recommended cell for extended cell life. I just don't know if there's a linear relationship between chlorine produced and cell life.

---

I guess that's the key to my question; are there higher CL losses at a given CYA level when trying to maintain a higher CL level. If that is the case, then I should aim for the lower end of the recommended range.

Quote:

---

Originally Posted by mas985

The % setting of the cell will depend on chlorine loss because that is the chlorine you are replacing every day.

Also, SWG cells are usually rated in amp-hours. So it is both the time the cell is on and the current running through the cells. Higher salt levels creates more chlorine but also higher amps (Goldline cells) and it is somewhat linear so that should be a wash because the higher chlorine levels means a reduced run-time (%).

Cell life seems to also be dependent on the chemistry balance. This is why some SWG owners experience very short cell life while others are much longer.

---

My first inclination is to say that the actual CL level being maintained doesn't impact cell life, its the amount of CL loss each day that has to be replaced that impacts cell life. But if what BigDave said is correct, then trying to maintain a higher CL level will result in higher losses each day, thereby directly impacting cell life. I'm not so sure this is the case though. After keeping my pool at shock levels (20 ppm) until combined CL was gone, I let it drift down to 5 ppm before turning on the SWCG (it was mostly cloudy during that time so it took almost a week). I tested the CL level each evening and the rate of decline was pretty steady, about 1.5 ppm each day. It didn't drop faster in the beginning then slow down as it dropped as BigDave's information would suggest.

I do understand that water chemistry is a factor as well, but with this question I'm only trying to find out if the CL level maintained is a factor as well.

I greatly appreciate the feedback.

Theoretically, it should be exactly the same. A 10% increase in CYA gives 10% more UV protection so the FC residual should rise by 10% countering the 10% increase in CYA (i.e. same FC/CYA ratio). So it should all net out to exactly the same % SWG setting and the same cell life. This of course assumes that it is only UV which is destroying the FC.

My own experience has shown that this is true and in fact, there may be a little extra benefit with higher CYA. In some cases, when I went from a low CYA to a higher CYA, I was able to actually lower the SWG % settings to achieve the higher FC levels. Based upon this, it would appear that the UV protection properties of CYA are somewhat non-linear.

Quote:

---

Originally Posted by mas985

Theoretically, it should be exactly the same. A 10% increase in CYA gives 10% more UV protection so the FC residual should rise by 10% countering the 10% increase in CYA (i.e. same FC/CYA ratio). So it should all net out to exactly the same % SWG setting and the same cell life. This of course assumes that it is only UV which is destroying the FC.

My own experience has shown that this is true and in fact, there may be a little extra benefit with higher CYA. In some cases, when I went from a low CYA to a higher CYA, I was able to actually lower the SWG % settings to achieve the higher FC levels. Based upon this, it would appear that the UV protection properties of CYA are somewhat non-linear.

---

In reference to my question, the variable is the desired CL level, not the CYA level. Assuming CYA is kept at the top of the recommended range for my SWCG (80 ppm), do you think there would be any difference in swcg% settings whether maintaining CL at 4 ppm or 8 ppm?

Thanks. :)

For the same CYA level, higher CL levels require higher % setting or longer pump run time. How else would you get the higher CL level?

Quote:

---

Originally Posted by mas985

For the same CYA level, higher CL levels require higher % setting or longer pump run time. How else would you get the higher CL level?

---

Keep in mind I'm just talking about maintaining a given CL level, not increasing the level (liquid CL can be used to get to the target level).

On the surface it seems maintaining CL level just requires the SWCG to generate enough CL to replace what's lost. If true, then the SWCG% and runtime should be the same whether you're maintaining 4 ppm or 8 ppm (CYA woukd be kept at 80 ppm) assuming CL loss is the same at both CL levels. However, if CL loss is greater when trying to maintain the higher CL level with a set CYA level of 80 ppm, then the SWCG would have to run longer and/or higher %. I'm trying to figure out which of these is true.

My recent experience with the CL level dropping at an even rate each day (1.5 ppm per day) from 20 ppm to 5 ppm (CYA remained at 80 ppm) suggests that the rate of loss isn't faster at higher CL levels.

I hope I'm making sense (it makes sense in my own head....lol). :)