effect of high CYA on Salt levels with SWG

[tim_schandorff]

I was recently away from my pool for about 6 months and during that time a friend was taking care of the pool. When I returned he said that he kept adding salt but the salt level on the SWG (Hayward aquarite 40k) never came up above the required minimum so he just added granular chlorine instead to bring the FC level up. When I got back I did some more in depth thesting than he had done and found that while the SWG is reading low levels of salt a strip reads that it is above 6k ppm. I also tested the CYA levels and they are well above 100ppm (not sure exactly because the CYA tester only goes to 100ppm). would you expect that the Granular chlorine he was adding had stabilizer in it? is there any way to fix this issue other than water replacement (I have to pay a lot for water where I am)? and how should I bring up the chlorine levels in the meantime so I don't add more stabilizer? The SWG still thinks it has to little salt so it is not generating.
Thanks for the info.
Tim.

 

[JasonLion]

The only practical ways to lower either salt or CYA is to replace water or get a reverse osmosis treatment (which is only available in a few places).

A SWG will report a much lower than actual salt level if the cell plates have calcium scaling, or if the cell has reached the end if it's lifetime. It is fairly easy to remove the cell from the plumbing and look in one end to see if there are any white chalky deposits. If so cleaning the cell (described in your SWG manual) should take care of it. If the SWG looks clean, chances are that it has reached to end of it's lifetime. Some pool stores can test cells to see if they are worn out.

Liquid chlorine (ie bleach) is a good choice for supplying chlorine in the meantime. It is readily available, not too expensive and won't add any more CYA.

 

[tim_schandorff]

Thanks for the quick reply. The cell was cleaned multiple times by my friend but I still need to check it for myself. He claims that there is no buildup. The cell is only about 2 years old and does not get as much use as most cells probably do since we don't have the constant supply of electricity that most places do. Either way my understanding was that you should get more than 2 years out of a cell. Is that correct?

Thanks for the help.
Tim

 

[JasonLion]

Typical cell life is 3 to 5 years, but it varies fairly dramatically. If your CYA level is lower than recommended, or you keep the percentage cranked up too high, they can last about half as long as usual. If the pool is a lot smaller than the cell is designed for they can last several times longer.

 

[chem geek]

would you expect that the Granular chlorine he was adding had stabilizer in it?

"Granular chlorine" or "chlorinating granules" is often Dichlor. Cal-Hypo is also granular, but that's usually not in the name.

For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm. So that's how your CYA rose -- from adding Dichlor. This is why you should normally add chlorinating liquid or bleach instead of other types of chlorine unless you intentionally want to increase your CH level with Cal-Hypo or your CYA level with Dichlor or Trichlor.