Pool algae issues - Water analysis

[DanGA]

Alright so I've been bustin my butt trying to get this pool water clean but havn't had any luck. For about 3 weeks I've ran the pump and keep backwashing. Yesterday I shocked it with 5 bags of shock hoping that would do the trick but no luck. I have been adding tons of bleach in there per a last forum and that didn't get me anywhere. I appear to have removed all of the leaves. Yesterday I also used some Wal Mart FLOC but I don't think that worked, the pool store said my chlorine is too high for it to work at the moment.

It is a 21 foot round pool 4 feet deep:

TDS 600
CYA 0
Total Chlorine 10 (evidently very high)
Free Chrlorine 10
pH 7.2
Tot. Alkalinity 92
Total Hardiness 106

I've been in the mindset of killing the algae killing the algae and really nothing else, am I taking the wrong approach? Any guidance would be greatly appreciated. [/img]

[chem geek]

Something is wrong with your numbers if you've had sunny days. With zero CYA, the chlorine would not last a day -- half gets broken down in direct noontime sun every half-hour.

You should get your own good test kit to make measurements yourself using the Taylor K-2006 kit you can get here or the TF100 kit you can get here which has 36% more volume of reagents so is comparably priced "per test" to the other link.

If you truly have no CYA, then you need to add some, but I suspect the CYA number isn't correct.

Richard

[DanGA]

I've messed with the pool quite a bit with other chemicals but never added any CYA. Does the CYA react with chlorine to make it stronger and ultimately kill algae and such? I've been reading a little bit about it, looks like it does rely on eachother but adding CYA will lower the PH. Thanks for linking those test kits, I'll definitely purchase one of those.

[DanGA]

disregard my last question I answered it by reading past threads

I'll bump up the CYA and cross my fingers that the green turns into gray.

[chem geek]

If you've ever used Trichlor pucks/tabs or Dichlor powder, then your pool probably has CYA in it. If you've only used Cal-Hypo or chlorinating liquid or bleach (or lithium hypochlorite powder) then you probably don't have any CYA in the water. I don't think you've been using Cal-Hypo since your CH number isn't high.

Just add a little CYA -- don't go above 30 ppm. HOWEVER, I would NOT trust your pool store -- get yourself your own test kit. Some pool stores INVERT the CYA number saying you've got 0 when you've got over 100 (some store employees aren't trained well). You only need a little to protect chlorine from rapid breakdown from sunlight. You can most easily add CYA AND chlorine together easily by buying Dichlor powder and adding 10 ppm initially, then when the FC drops add another 10 ppm and then another until you reach cumulatively 30 ppm which will give you 27 ppm CYA which should be fine. Then switch to chlorinating liquid or unscented bleach after that. If you already bought pure CYA, you'll need to hang it in a sock or panty hose over a return flow and it will take a couple of days to dissolve -- that's why I suggest the Dichlor since it dissolves right away (though you still can't add it all at once).

Even so, you'll need to add chlorine multiple times per day, especially the first day or two, as it will get consumed killing the algae. If the FC level gets too low, then the algae will grow faster than it gets killed. You have to keep the FC high to kill the algae. Have the FC level be 40% of the CYA level for a reasonably fast kill of the algae, so maintained at a minimum of 12 ppm FC with 30 ppm CYA for example. The key is persistence.

Even pools with lots of algae can be cleared with chlorine alone as shown in this link.

Also, if you truly have algae, then you shouldn't be seeing high FC except immediately after adding it. The FC should drop fighting the algae. If the water were clear green instead of cloudy green, then it could be copper instead of algae, especially if it got more green after adding chlorinating liquid or bleach as that raises the pH precipitating out more copper.

Richard