algae nightmare

[rural pool]

This year we are fighting green algae and have read many of your articles that is helping. But we need more help about the next step. We have cleaned the pool and slammed it with 14 pounds of cal-hypo (57%) and the algae was still green when the pool was vacuumed. Two days later, last night, we slammed it again with 12 pounds of cal-hypo (73%).

Here are our current readings:

FC - 11
CC -.4
CH 150
CYA - less than 10 (if accurate because of algae)
TA - 80
PH - 7.2

Right now the pool is cloudy blue, so what is the next step?

 

[phibroptic]

What are you using to test the water?
The CYA test is usually only accurate to 30ppm, anything below could be 0 for all you know. If so, the sun is burning off chlorine as fast, if not faster, than you can throw it into the water!
Even though CH isn't really a problem with a vinyl liner, I would transition from cal-hypo to liquid chlorine to avoid adding more.

The CYA/FC chart found here recommends a shock level of 10ppm FC for the SLAM procedure, if you have a CYA of 20ppm (it doesn't go to 10, if that number is accurate.)

Are you familiar with the SLAM Procedure?
Time and attention will get everything cleared up, you just need to stay at or above the recommended Shock level for your CYA (don't go too far over, or you may fade the vinyl liner) until you meet 3 criteria.
1. CC <= 0.5
2. Pass an OCLT (Overnight Chlorine Loss Test, where FC drops 1 ppm or less overnight, when the sun isn't burning it off.)
3. Water is crystal clear (If you question it, you should be able to throw a quarter in and tell if it lands on heads or tails. A trick one of the mods taught me a few days ago.)

So, aside from questioning your CYA level, and wondering if you might be better of raising it a bit (carefully, as it is painful to lower it) I think you just need to closely monitor a SLAM, and you should have nice results!.

 

[Isaac-1]

You should also be aware that Cal-Hypo can cause water clouding under some conditions this is why we suggest bleach / liquid chlorine. Also a key aspect to the SLAM process is the M which is MAINTAIN meaning to keep your FC at Shock level and NEVER let it drop below that until clear. What you have done is just give it a couple of swift kicks then walked away and let the algae come back.

 

[tim5055]

phibroptic has it covered pretty well, but I want to reinforce - A SLAM is a continuous process of adding chlorine to a pool multiple times a day over multiple days until the pool is completely clear/clean, not a one time addition of chlorine. Additionally, you should be using liquid chlorine; (8.25% bleach or 10/12.5% chlorinating liquid). Solid forms of chlorine are adding things you may not need to your pool.

 

[rural pool]

I use the Taylor K-2006 Complete FAS-DPD chlorine kit. The CYA is not showing up at all on the 30ppm. Would you use bleach to shock? Also I was reading the article about borates and thinking that adding this might help? I am brushing every day and the filter has been on for 6 straight days.

 

[tim5055]

Ignore borates, they are an option when you have a clear pool, not something that will help clear up a pool.

Bleach or higher % chlorinating liquid is what you want.

 

[Defgufman]

Yes use bleach for the FC. Only regular unscented 8.25%. Borax for ph increases, don't convert to a Borat pool till you complete the SLAM.

 

[phibroptic]

The CYA is not showing up at all on the 30ppm.

Does the 7ml pool water, 7ml reagent mix get cloudy at all when you run the CYA test? If not, your CYA is probably 0 or very close. If it does get cloudy, then all we know is that it is <30ppm, which makes it hard to maintain a constant FC level required for the SLAM. If you do add CYA, it's best to under-dose what pool math recommends, because it is easier to add than remove. And, very important, it can take up to a week to register on the CYA test. So, calculate, pull the calculation back a bit from your desired level, apply the CYA, wait a week, test the level, repeat if necessary. The most common application method suggested on these boards is to put the CYA in a sock, and tie it off in either the skimmer or in front of a return jet, and squeeze the sock periodically to help it dissolve.

Would you use bleach to shock?

Standard bleach, as others have chimed in, is all you really need for shocking as well as standard chlorine maintenance.
Standard bleach, or higher concentration liquid chlorine that is sometimes called "liquid shock" or something else, should only have sodium hypochlorite as the active ingredient. That is sodium and chlorine combined. The "hypo" in the cal-hypo you have been using is also hypochlorite, just bonded with calcium instead of sodium. All solid forms of chlorine, as a rule of thumb in general, contain "extra stuff" that you don't want in your pool. For example, the Hayward Chlorinator you have uses trichlor tablets. Those tablets add chlorine, as well as CYA to the water. Too much CYA renders the chlorine unable to kill things in your pool without reaching insane levels of FC. It is also why the pool I bought in January had over 200 ppm CYA, and I had to drain and refill a portion of the pool 7 times to get down to a more reasonable level of 40-50 ppm. (The previous owners left a giant tub of tablets for me, too. How nice of them! )

The TFP method relies on not adding "magic" pool store ingredients that add extra chemicals you don't need, because they usually do more harm than good. It shoots for the purest form of what you need, while still being easily attainable. (Straight chlorine gas would be the most pure form you could use to chlorinate your pool, but getting, storing, and applying it is very difficult, complex, dangerous, and in some areas, illegal.)

 

[rural pool]

I understand the CYA dilemma that is why I am not using the chlorinator right now. I put 40 oz. of stabilizer in three days ago but I had to backwash and vacuum to waste so I do not know how much I lost. The pool only had 19 inches of water this year when we filled it. So most of the water is new in it already.

 

[rural pool]

When I put the water and reagent in the tube it is a little cloudy. I understand the dilemma with the CYA and that is why I have not filled up the chlorinator yet. I put 40 oz. of stabilizer in three days ago but I had to backwash the filter and vacuum to waste because of the algae. So, I do not know how much stabilizer that I lost. My question is what should the shock level be if I do not know an accurate reading on my CYA? In addition how much granular stabilizer should I add?

 

[paigenicole0289]

I would maintain your SLAM level at the number which you added to using pool math. So if you added enough CYA to get it to 30, assume its 30 and use that as your SLAM level.