Shocking With Liquid Chlorine

[aGrandma]

I've been posting on the "inground pool" section and just noticed this "water chemistry" area. My problem should be here.

I have an inground 15,000 gallon gunite pool with a salt water chlorine generator. I've been dealing with algae for over a year. I have spend hundreds of $ at the pool supply store and it seems to clear it up for a few days but it always comes back. After posting on this board I am now shocking using chlorine bleach from the store (6%) and using the chemical form on this forum to calculate how much bleach to use.

2 nights ago I used 5.5 bottles of the bleach. My water is crystal clear but there is a little green on the walls. I have a regular paper filter system (not sand), which I cleaned yesterday and have kept my pump running. I added another 1.5 gallons of bleach yesterday....

Today my chemistry is at FAC = 5 and CYS = 50. According to the chemical calculator I should add an additional 5.5 bottles to keep the level of shock up?

Am I doing this right? Am I supposed to try to get that number 5 up to a number 24??? That sounds impossible. How many bottles of bleach will I go through in 2-3 days of this? When I started I thought I'd go through 7 or so total...Will I actually go through more like 20? Or am I doing the calculations incorrectly?

And when do I know when it's done? When the walls are completely clean and white? I have been brushing them at least 2X per day.

And last, I found some black algae under a plastic drain cover. I removed it and brushed it off. At the pool store they told me that has to be treated with "black algae remover" or copper-something...Is that true or is there something else I can use to get rid of it? Or is brushing it off good enough? It also might be what is on my tile grout which I have been scraping off too. (Yes I am stiff and sore all over.)

[polyvue]

Am I doing this right? Am I supposed to try to get that number 5 up to a number 24??? That sounds impossible.

No, you're not doing it correctly. You need to target a high chlorine amount based on current level of CYA. 5 PPM FC is likely not even close to your goal. If CYA is 60 PPM, you should aim to put enough chlorine in the pool AT ONE TIME to bring it up to 24 PPM FC. If you just throw in a few bottles here and there without frequent testing and adding more bleach whenever the Free Chlorine drops below 24 PPM you'll be doing this forever and probably still have an algae problem.

How many bottles of bleach will I go through in 2-3 days of this? When I started I thought I'd go through 7 or so total...Will I actually go through more like 20? Or am I doing the calculations incorrectly?

What is the numer of ounces in these bottles? 96 oz jugs? Are you using bleach identified as "6% sodium hypochlorite" or is the label missing the percertage? Seven (7) 96 oz. jugs of 6% bleach should add 20-22 PPM chlorine to the pool. But you'll have to have additional jugs in reserve so that you can add more throughout the day --- whenever your test results indicate that the chlorine has come down from your target of 24 PPM.

And when do I know when it's done? When the walls are completely clean and white? I have been brushing them at least 2X per day.

Once the walls are clean and white (and the water is clear) perform an Overnight Chlorine Loss Test. This will be the criteria to tell you that you're finished shocking.

I'd encourage you to not give up... stopping too soon may allow the algae to return. You've been fighting this for a year according to your post. Time to finish it off. Good luck.

[aGrandma]

I think I "got it" now!! Thanks for the encouragement and information. In theory, when I began the calculator told me to add a certain number of ounces of 6% bleach, and I did - at that point if I tested it, it should have been at the target level of chlorine, correct? But by the next day when I took the sample to the pool store it was already down to 5. I should have been adding bottles as needed to KEEP the level up at 24. (The pool store guy told me that 5 was a good shock high enough to kill algae!) At that point I thought I was not understanding the chemistry calculator - I thought there was some additional calculation that needed to be made - I guess NOT!

My pool walls are very clean and white now - my water crystal clear. I have not seen my pool so pretty since I can't even remember! I will perform the overnight chlorine loss test tonight...

I bought a new steel bristle algae brush that connects to my long handle - that works GREAT. Before I was using nylon brushes, and it was doing nothing but wearing me out.

If this does not work, now I know what to do. Probably buy the test kit so I have it at home and buy lots of bleach to have on-hand to keep the level super-high!

[aGrandma]

I have been taking my water to Leslie's Pool Supply every day for testing since I began the shock process. My chlorine went from 2 ppm to 5 ppm and never higher. I talked to the guy at the store today and he told me that their test equipment does not go higher than 5 ppm!!! So I might have been up at 24 or 20 or 32 ppm but I never would have known it!!!! I have to get the Taylor k-2006 and do my own testing from home. I ASSUMED the pool store would use the BEST test equipment!!??!!

[chem geek]

I ASSUMED the pool store would use the BEST test equipment!!??!!

Pool stores are notorious for doing the tests incorrectly or not calibrating their equipment or using the best equipment or training employees well on how to use them, etc. You are far, far better off getting your own good test kit and testing yourself.

[polyvue]

I have been taking my water to Leslie's Pool Supply every day for testing since I began the shock process. My chlorine went from 2 ppm to 5 ppm and never higher. I talked to the guy at the store today and he told me that their test equipment does not go higher than 5 ppm!!! So I might have been up at 24 or 20 or 32 ppm but I never would have known it!!!! I have to get the Taylor k-2006 and do my own testing from home. I ASSUMED the pool store would use the BEST test equipment!!??!!

As chem geek noted, pool store testing can be unreliable. They are all over the place in their testing methods and outcomes. My local Leslie's uses the DPD Chlorine method found in the Taylor K-2005 complete test kit -- it's arguably better than using OTO (yellow color) or test strips but the chlorine test found in the K-2006 delivers more precision, is easier to use and works at very high levels of chlorine. This all translates into control over outcome.

Store personnel seem to be entirely uninformed of any relatiionship between Cyanuric Acid and Free Chlorine levels. I've heard them instruct customers having issues with algae to lower their chlorine and use phosphate remover because of "chlorine lock". Amazing! Of course, they haven't received any education in pool chemistry (beyond basic titration techniques) that would allow them to help customers with problems; it must be a frustrating job.

Just think how many dollars you can save this summer by procuring a K-2006 (FAS-DPD) kit from a discount vendor and doing your own testing. And, needless to say, it's also nice having an algae-free pool with clean water and the knowledge to correct problems before they become serious.