As noted in this link, this sequestering agent breaks down in sunlight with a half-life of only 5 hours using a Xenon lamp. In another test using actual sunlight, the product lost 88% after 50 days (at pH 7). In a lake test, the half-life was 7 days. This is NOT designed to be used in outdoor environments, for sure. Unfortunately, most phosphonate metal sequestrants have this problem depending on concentration and if metals are present -- even HEDP that I normally recommend can break down if there's a lot of iron present, but it's normally reasonably stable and somewhat slow to break down from chlorine as well.
I'm not clear on what the phosphates have to do with the problems you are seeing anyway. So long as you have Free Chlorine (FC) in the water (high enough relative to CYA, if used), you should be killing off both algae and bacteria. The only issue with chlorine demand I could see would be if you had biofilms in the sand filter, for example, in which case if you had lower phosphates then such growth might be slowed down once you remove them.
Thanks for the input Richard!
In my last post I neglected to summarize why I referred to 3ppm phosphate as being a problem. Al & Tom had discussed (phone & email) that the enzymes had consistently been less effective in pools that had high levels of phosphates present in the water, and on that same note, Al showed me some before & after pictures of pools in our part of the State with phosphates present and phosphates removed. With phosphates present, the pools looked dull and discolored, even though all of the other numbers checked out OK. Once the phosphates were removed, the pools looked exactly as they should - sparkling, crystal clear water. Al, correct me if I am misquoting you on any of this - it was a lot of information exchanged in one conversation!
To make a long story short, our pool now looks a lot like the ones he showed me with phosphates present (and given its 3ppm result, I would believe the test confirmed that).
So in the short-term, we're tweaking the dosage of the enzyme with phosphates both present and removed to have the numbers to either confirm or refute the effect of phosphate on the enzyme's effectiveness. We will also then know how much of an effect the presence of phosphate affects the appearance of our water. Given our bather loads, I am confident it will help but not fully solve its appearance.
Given that it's an indoor pool, algae is not an issue given the FC residuals, and there's no CYA present thanks to WI state code (outdoor pools max CYA is 30ppm, indoor 0).
Hopefully that clears up that part in the near-term. If I go dark on the subject for a while, it's because I don't want to jump to conclusions until everything has been tried and documented - I'd rather give everyone full results on the subject once it's all said and done.
At each stage of the process I intend to take pictures of the pool to accompany all of the numbers, and hopefully the results will give us a clearer picture of what works vs. what doesn't.
Again, thank you all for your input!
Aaron, I think you're on the right track here with your conversation with Al and myself. In a nutshell with pools with lower phosphate readings (500 ppb or less) we see a greater impact by the enzymes on combined chlorine. I don't have enough "science" behind my theory the enzyme has an ability to catalyze the combined molecule if you will, but am comfortable with this statement based on my field experience. I also feel reducing demand IE organics(greases & oil) as well phosphates really improves the efficiency of the sanitizer.
Had difficulty adding attachments with my I-pad. Anyway, here are the pics.
First one is how manganese water comes in around here. Dark grassy green.
2nd pic is treated with Sea Klear, (chitosan), followed by shock dose of chlorine. Turns this color in about 20 minutes. The pool is sparkling blue, usually in 24 hours. Backwash water is black almost.
3rd pic is the lime green due to city water phosphates. Shocking and Sea Klear only lightens it somewhat. Takes about 3 weeks to gradually turn blue.
Thanks for clarifying that - I knew I had my lines crossed somewhere, and that was it - when you were talking about the SeaKlear and the metals, somehow I had gotten the phosphates stuck in my head.
As far as I can tell, the Jury's still out on the source of the dullness, as we were only using Calhypo to periodically shock the pool, and the Calcium hardness is in the low 600's. The large pool, which still has that clear "vibrance" had also been subject to periodic calhypo shocking, and the hardness right now is in the low 700's. I think there must still be something to do with the bather loads and the dullness, as the facility was only open for 4 hours yesterday, with a total bather load of 14. This morning the pool actually looked like something we'd want to swim in! By the time the day camp kids were in there for 2 hours, all bets off.
TDS on the small pool is at 1300, and over 1600 on the large pool.
Sorry about crossing the lines on the phosphates, and I hope that didn't lead anyone else to think that the dullness may come from them. For a while I had myself convinced of that, and without your clarification I don't know how much time I would have spent chasing it.
In any case, from my recent experience with using the SeaKlear PRS exclusively to remove metals when filling our whirlpool (and it was less than 5 hours for all discoloration to go away), I'm willing to use the same method on the other 2 pools in August. In the summer when the city is actively flushing the mains, the water comes in really clear, so as long as we're not filling one of the larger pools in Winter, the metals aren't nearly as much of an issue.
Once we have a phosphate test kit (July 23), we'll know if the fill water does indeed contain them or not.
Until then, thank you again for weighing in and catching my goof!
Have a great weekend!