Scaling on cell...why?

[JimK]

#1 is likely your problem. SWGs can easily scale if the CSI (calcium saturation index) gets too high. You are better off with a slightly negative CSI to keep the scale off. You can use the poolcalculator.com to figure out your current CSI.

Also as cells age, then tend to accumulate more scale. I would avoid scraping the scale since that could also scrape the cell coatings. You are much better off using acid to clean cell then any mechanical method.

Thank you for the information and suggestion on how to clean the cell.

Are you saying that allowing pH to get up to 7.7 is an issue even though its still considered in the normal range? Should I go back to adding acid whenever pH reaches 7.6?

I played around with the pool calculator using a variety of levels in each field my pool might see throughout the season and found the CSI varied between -0.74 and -0.02 (it always came out in the negative).

[mas985]

The "correct" PH depends on other factors like TA and CH which is why I suggested the calculator. However, having a negative CSI does not guarantee a scale free cell, only reduces the likelihood. You could try lowering the PH a little and see if that helps (i.e. keep CSI between -1 and -0.5) which should not be a problem since you have a vinyl pool. Also, it would be a good idea to make sure you are actually getting scale and not something else. Scale is indicated by fizzing when immersed in a acid solution.

[JimK]

The "correct" PH depends on other factors like TA and CH which is why I suggested the calculator. However, having a negative CSI does not guarantee a scale free cell, only reduces the likelihood. You could try lowering the PH a little and see if that helps (i.e. keep CSI between -1 and -0.5) which should not be a problem since you have a vinyl pool. Also, it would be a good idea to make sure you are actually getting scale and not something else. Scale is indicated by fizzing when immersed in a acid solution.

Thanks for the advice on where to keep CSI. Having that range to shoot for is helpful. Right now I'm at -.77. Using the calculator it's interesting to see how much effect temperature has on CSI. Something else I think should help is I expect my CH level to drop since I do not plan to use cal hypo this season, just plain bleach when I need to shock.

Regarding the use of Jacks Magic Purple Stuff, do you think it is helpful in preventing scaling?

If I see more "scaling", I'll take a sample and put it in some acid solution to see if it fizzes like you mentioned.