Quote Originally Posted by maglib View Post
Thanks again. So where would you recomend I keep my chlorine levels at?
You need to follow the Best Guess chart . . . which means your correct FC levels are determined by your CYA level. Keep in mind that if your CYA level is below 40, you'll have high chlorine loss to sunlight.


Why would I get small black spots in my plaster if the chlorine is at 2 like it is and I have the SWG and the mineral cartridge?
Your spots could be:
#1 - black algae, OR
#2 - copper oxide staining on some element in the pool coat, OR
#3 - something else.

To test for black algae: get a plain uncolored toothpick -- preferably flat -- and scrape off a bit of the black spot. If you can not do so -- it's not black algae. Smear the bit you scraped off on a white piece of paper -- a 3 x 5 card is perfect, then use a knife or spoon to spread it out. Black algae, spread thin, will be dark green. If it's any other color, it's not black algae.

To test for copper stains: put a vitamin C tablet on one of the stains. If the vitamin C lightens the spot, it's probably copper.

If both tests fail, we'll have to re-think.

But you seem to have some misconceptions about your equipment:

+ Most 'mineral' units do nothing. Those that 'work' add enough copper to cause staining. A few still include silver, which WILL cause black stains, but usually not localized ones.

+ Contrary to what many people think, a salt system (SWCG => Salt Water Chlorine Generator) is nothing more than a way to add chlorine to your pool. With an SWCG, an electrical current is passed through a solution (pool water) containing sufficient salt (chloride - Cl-) so that chlorine (Cl+) can be generated.

+ Phosphate removers are occasionally helpful, always messy, but never essential.

+ Adequate chlorine levels MUST be determined by the Best Guess chart, which sets chlorine level based on CYA level.

+ To PREVENT black algae, simply maintaining correct chlorine levels, per the BG chart is enough.

+ To CONTROL black algae, once established, it's necessary to maintain shock levels (BG chart again) for long periods of time AND to brush the areas where algae appears.

+ To ERADICATE black algae -- on concrete pools -- usually requires draining the pool.