Green Algae

[lynn2_cal]

This is my first time writing, but I've been reading for the past year since we had our pool put in a year ago. Everyone is so helpful and I have been able to find my answers by reading other's problems. So everyting has been great so far but now I need to know if I'm on the right track or need to drain 1/2 and refill to get my CYA down.

I have a 7500 gal IG pool, with SWG and solar. Water temp is upper 80's. I regularly only add M. acid and 7oz. of some stuff advised by Gemstone people to keep calcium from forming.

I have a cartridge filter that was just cleaned after using PhosFree to get my 1,000+ppm phosphates under control. (This was in the beginning of my battle with the algae and what was reccomended by pool store.) Later I read this was not necessary since I still have the algae problem!

I'm still fighting green algae. Not bad, water is clear, but there are areas where you see it on the walls and my skimmer socks are green when I take them out to clean.

After much reading I had my water tested at pool store since I don't have a test for CYA:

FAC .5
PH 7.8 (before adding 2 cups M. acid)
TA 60, (I tested it at home at 100)
CYA 100

Yesterday, after checking with Ben's Best Guess CYA table, I added 1 1/2 gallons bleach, and then before bed another 1 1/2 gallons. Using the shot glass method I figured my FAC at 27ppm, which with a CYA of 100 I needed it up to 27ppm. Correct?

I've also just read that it's bad for the TAC to be higher than the FAC. I didn't know that and that has always been the case.

Now this morning my FAC hasn't gone down so I haven't added anything more but I noticed my skimmer socks are light green again. Does this mean the algae is still alive or just getting filtered out of the water? How do you know when the algae is dead or alive. I will keep an eye on the chlorine and keep it up around 25. How may days?

Is this the correct battle plan?

Thanks in advance





Now this morning

[duraleigh]

Hi, Lynn,

I assume from "Gemstone" that you do not have a vinyl liner...correct?

[lynn2_cal]

correct, it a pebble finish

[duraleigh]

Your CYA is very high. I would take the Cl ppm up to 30+ to insure you have reached breakpoint. That will most likely clear the algae from your pool. Be persistent with the high Cl until your water shows no trace of algae.

FAC(FC) is free chlorine that's good for your pool. CC is combined chloramines that don't do any good but are still there. When you test for TAC (TC), you get the total of FC and CC.

By shocking your pool, (30+) you will get rid of the CC's and your FC and TC results will be the same number. Your pool will clear up as well.

I'm assuming you don't have an SWG.

Your high phosphates may be contributing to your propensity to grow algae...I have no experience and cannot comment on that other than to say high Cl levels are the best preventative.

Lastly, consider draining 1/2 your pool...maybe twice. That's not too much water and it may give you a fresh start on CYA levels and reduce the phosphates.

[lynn2_cal]

Thanks,

yes I do have a SWG. Should I wait to drain 1/2 as a last resort? Will it hurt anything with the chlorine up at 25 to turn off the pump if I drain?

[duraleigh]

Thanks,

yes I do have a SWG. Should I wait to drain 1/2 as a last resort? Will it hurt anything with the chlorine up at 25 to turn off the pump if I drain?

Hi, Lynn, Yeah, that changes somes things...I should've asked you that first. Yes, drain as a last resort.

Leave your CYA up there at 100...it's alittle high for SWG, but it'll dilute with rain and refill.

Still shock the pool as in the earlier post. That'll clear your water, get rid of the CC's and not put a strain on your SWG by asking it to do it. (They're not really good at shocking.....particualrly those high levels.)

Still can't comment on the phosphates...I have no experience

[lynn2_cal]

Thanks again duraleigh,

I tested again and chlorine was down to 18, added 1 1/2 gallons bleach per bleach calc. to get up to 30.

I'm not worried about the phosphates now either. They were way down after adding the PhosFree.

[lynn2_cal]

Other questions, do I need to keep the chlorine up around 25-30 for a week? I'm not seeing any algae this morning, it's been 2 days now with pump running 24/7.

Again, how do you know algae is dead?

Can I run my navigator in water with that high of chlorine?

[duraleigh]

Lynn,

Reduce your Cl back when you can hold FC overnite.

Test in the evening, bring up to 30, test before the sun hits it in the AM.
Unless, your AM reading is, say, 28 or better, your still consuming organics in your pool.

That's your guideline to drop back to the 2-4ppm that your SWG probably recommends .

I leave my auto-vac in the pool most of the time...including shock levels. No harm so far, but mine's not a navigator.

[lynn2_cal]

Thanks for the quick answers
With a CYA of 100, don't I need to keep my chlorine levels higher?

[duraleigh]

With a CYA of 100, don't I need to keep my chlorine levels higher?

You'll need to get that info from the SWG manufacturer. I know they are quite comfortable with maintenance Cl levels much lower than with ordinary chlorination.:)