Pool Store Test Worthless/cya High Need Advice

[largen101]

Well I bought this house in June of 2005 and just did what the pool store said for the rest of that summer. In the winter I read bout BBB etc.., but was too lazy to look into it further. After a much higher then expected pool cost (go figure) the summer of 2006, I was fully ready to implement the BBB. I opened the pool and had it clear with in days and it was going great. I used up some Chlorine tablets I had left and started in on the bleach. I left on a four day trip and came back and the pool was cloudy. I hadn't gotten a test kit yet so I still relied on the pool store and their wonderful Biogaurd software and color strip coumputer test. I have been literally dumping bleach in this pool and nothing has happend, I kept going to the pool store and the test all looked good. My own test kit finally came and I did my own test. I should add that their test had my CYA at 30 and I wanted it a little higher so I added 4lbs or Cynuric Acid. I don't know what their test was doing, even after I added the stuff it showed CYA 30. My first test of my own shows the CYA at 90-100! So I was already high and then made it worse. Curently here are my numbers

FC 30-40ppm

CC 0ppm

TC 30-40ppm

PH 7.4-7.5 although this is probally worthless right now with TC so high

T/A 170

CYA 90-100

So the whole time I am wondering what is wrong cause I didn't think I had mustard algae, well know I know my CYA is so high it is killing me.

My pool is a 30,000 gallon concrete pool. I am going to get some Polyquate or whatever and add that to try and help, but I refuse to spend the money on the amount of bleach it will take to keep my TC where it needs to be with this high of a CYA. I need to at least cut it in half so do I need to drain out half the pool!!!!

Any help would be great!!

At least I wasn't buying pool store chemical and feeding their pockets by just burning up Chlorine

Thanks

[chem geek]

If water is relatively cheap for you, then doing a drain/refill to get your CYA level down is the way to go. You'll then need less Free Chlorine both for shocking and for maintenance. The higher CYA does help protect the chlorine from degradation from sunlight so there is a bit of a tradeoff in terms of how much chlorine loss there is, but getting down to 50 ppm CYA or a bit lower will certainly help. If your pool is cloudy, then it's probably just nascent green algae. Yellow/Mustard algae usually shows up on walls and the floor, not free-floating, and usually starts on the shady side. So with green algae, the shock level at 50 ppm CYA is 20 ppm FC while at 30 ppm CYA it's 12 ppm FC. As for maintenance, shoot for 5.7 ppm (3.7 ppm absolute minimum at all times) FC at 50 ppm CYA or at 30 ppm CYA it's 3.5 ppm (2.2 ppm absolute minimum at all times) FC.

If PolyQuat 60 algaecide is inexpensive for you, then using a maintenance dose of that will act as insurance in case you ever let the FC level drop too low. Up to you.

Richard

[chem geek]

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[largen101]

If water is relatively cheap for you, then doing a drain/refill to get your CYA level down is the way to go. You'll then need less Free Chlorine both for shocking and for maintenance. The higher CYA does help protect the chlorine from degradation from sunlight so there is a bit of a tradeoff in terms of how much chlorine loss there is, but getting down to 50 ppm CYA or a bit lower will certainly help. If your pool is cloudy, then it's probably just nascent green algae. Yellow/Mustard algae usually shows up on walls and the floor, not free-floating, and usually starts on the shady side. So with green algae, the shock level at 50 ppm CYA is 20 ppm FC while at 30 ppm CYA it's 12 ppm FC. As for maintenance, shoot for 5.7 ppm (3.7 ppm absolute minimum at all times) FC at 50 ppm CYA or at 30 ppm CYA it's 3.5 ppm (2.2 ppm absolute minimum at all times) FC.

If PolyQuat 60 algaecide is inexpensive for you, then using a maintenance dose of that will act as insurance in case you ever let the FC level drop too low. Up to you.

Richard

Water can't cost as much as the 50+jugs of bleach I have dumped in this hole in June. I retested the CYA it is actually over 100 past any form of measure I would guess 110-130. I have had that high of chlorine in it for awhile and the green color is still there it hasn't even faded out blue yet. This has to be the CYA not allowing the Chlorine to work isn't it?

[chem geek]

At 120 ppm CYA, it would take a shock level of 47 ppm FC to clear the pool relatively quickly, and that assumes you lower the pH first (to 7.2 or so) before adding the chlorine since that much chlorine will raise the pH quite a bit. And you'd have to maintain that level, or at least 30 ppm FC, the entire time. It's a real chore and usually the advice when the CYA is that high, especially over 100, is to drain and refill and not try to win the algae battle until the CYA is lower.

So in some sense you are right that the higher CYA is tying up more chlorine, but it's not ALL tied up -- it just takes more chlorine to overcome it. Roughly speaking, it's a ratio of CYA to FC that is important and at a pH of 7.5 it takes an FC level around 40% of the CYA level. Then, for maintenance, it takes an FC level of around 11.5% of the CYA level. At any rate, doing a drain and refill to get the CYA lower is your best option.

[largen101]

At 120 ppm CYA, it would take a shock level of 47 ppm FC to clear the pool relatively quickly, and that assumes you lower the pH first (to 7.2 or so) before adding the chlorine since that much chlorine will raise the pH quite a bit. And you'd have to maintain that level, or at least 30 ppm FC, the entire time. It's a real chore and usually the advice when the CYA is that high, especially over 100, is to drain and refill and not try to win the algae battle until the CYA is lower.

So in some sense you are right that the higher CYA is tying up more chlorine, but it's not ALL tied up -- it just takes more chlorine to overcome it. Roughly speaking, it's a ratio of CYA to FC that is important and at a pH of 7.5 it takes an FC level around 40% of the CYA level. Then, for maintenance, it takes an FC level of around 11.5% of the CYA level. At any rate, doing a drain and refill to get the CYA lower is your best option.

The pool is about drained to where the shallow end is showing, I am going to go vacuum to waste while the water is lower since it will be easier. I will get everything cleaned up nicely, then begin to fill back up keeping chlorine in it. I will get a new CYA reading when full and go from there. How the hell did the pool store say it was at 30!!

[chem geek]

Some pool stores have been known to take the reading and subtract it from 100. Others don't wait long enough for the turbidity test to fully form (mixing for 30 seconds). It's always best to test the water yourself and now with your Taylor K-2006 you can test everything you need accurately.

[itabb]

At my pool store, they are inconsistant in the way they test. Both my pool and spa are at 50 CYA, and they read 25, 40, and 90. They don't take it seriously. They see my pool is at 5+ FC and don't bother diluting to get a more accurate reading. I told them is was probably around 7, and I taught them how to use the titrate test. One of them got all excited about an electronic salt meter. It read 4400. My pool is at 3600. You think she put in a strip to verify? Nope, the eletronic meter must be right . . . it's new! They don't know the titrate end points either. The see TA turn from green to mostly red, and they're done. They don't realize they need to add 1 more drop so it is bright red and no longer changable. If I don't monitor their testing, I get wacky results.