Green pool and high CYA

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willhampton

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Aug 25, 2011
6
Round Rock, Texas
Is a partial drain *really* the only way to reduce a high CYA? Here are my current levels (using the TF 100 Test kit)
FC 33, CC 1, TC 33, CH1375, TA 120, CYA 100

I don't have a ton of algae, but have been struggling all summer to get the pool clear (didn't help that pump broke and had to be replaced). I've been using trichlor tabs and Leslie's Power Powder plus to shock the pool -- after really reading up on this site I understand that's not the way to go.

I don't have a drain in my pool, so will have to pump water out into the storm drain -- something I'm really not crazy about doing.

Will lots of direct sunlight reduce CYA? It's been an atypical summer here in Central Texas -- lots of rain and overcast skies.

Thanks for any help!
 
What does pool math say your CSI index is? If those numbers are correct for CH, you may be at risk of scaling if you keep using CalHypo shock, so keep an eye on that. You do need to drain and refill to reduce CYA, it is the only proven way. You can waste money on a bottle of false hope in the form of Bio-Active, but it isn't recommended.
 
Short answer: yes. You also need to drain to reduce that astronomical CH reading.

Before you start pumping, redo the CYA test using the dilution method (Post 8 Step 9) so you have a rough idea how much you really need to replace. You don't want to be one of the posters here who says "I drained half the water and my CYA is still 100."

You can use pool water on the lawn, or send it down the sanitary sewer if you're not on a septic tank. At least that way the neighbors won't see it.

If you have typical hard Texas water, you probably won't be able to get the CH down to suggested levels. But you need to get it down to at least half of what it reads now.

There's just no other way. Even if you do manage to kill the algae, you'll end up with coarse Calcium scale all over the walls - grow your own sandpaper that can leave road rash just by scraping a knee or elbow along the wall.
 
Thanks for the replies. I actually did the SLAM and it has succeeded. I did the CYA test using the dilution method and it is over 200. The PoolMath calculator now recommends an 80 percent drain. Ugh.

What is the problem with having high CYA? I'm guessing it means you have to maintain high chlorine levels to keep the algae away. Is that it?
 
Also SLAM levels are extremely high. If you've been using pucks, STOP, they just add more CYA. Make use of as much rain water as you can, it is CH and CYA free. So if you can divert roof gutters to the pool that all helps.
 
Well, I did the partial drain -- I would estimate 60 percent or so. My CYA is still pretty high (70-80), though I remember reading on one thread that it takes a week or so for the CYA level to settle. My new question is this: how accurate is the CYA test with the black dot at the bottom of the cylinder? Also, my TA is now at 170. Is that too high for a slam? Yes, I am having to slam again ...
 
Partial drain - great! :goodjob: 70-80 is still a bit high for a SLAM, but afterwards may work out just fine in our heat. There is no wait after a drain. The wait is only for when you add new stabilizer. As for CYA accuracy ... it takes a bit of practice. Mix the bottle, pour and view in the tube, and then pour it all BACK to the mixer and do it all over again with the same solution 2, 3,4 times to get a good feel and average. You'll get it. TA of 170 is a bit high, but a PH of 7.2 is more important right now to prepare for the SLAM.
 
willhampton said:
Well, I did the partial drain -- I would estimate 60 percent or so. My CYA is still pretty high (70-80), though I remember reading on one thread that it takes a week or so for the CYA level to settle. My new question is this: how accurate is the CYA test with the black dot at the bottom of the cylinder? Also, my TA is now at 170. Is that too high for a slam? Yes, I am having to slam again ...
Click to expand...
I'd question whether you really SLAMmed before. Shock level for 200 CYA is around 80 FC. :shock: How did you ever measure that? The FAS-DPD test is only good up to 50.

Perhaps you mean you "shocked" the pool the pool-store way, which is just one massive dose? That usually doesn't kill all the algae. It may kill a lot, but not all, and if the proper FC level isn't maintained (15 minimum for 200 CYA), it will grow and grow exponentially and you have an algae bloom again. Actually, the high FC levels the pool stores consider shock level are probably not even as high as what you should be maintaining. They tend to ignore the CYA level and try a one-size-fits-all approach.

High TA is no reason to delay a SLAM. Lower pH to 7.2 and do what you can to reduce aeration (eyeballs pointed down, for instance) and deal with the pH rise after the algae is gone for keeps and you have passed all three tests.
 

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I'm thinking not sorry. With a 60% drain and still that much Cya? I am not sure you even reached an adequate SLAM value for that much Cya. Where you are now is going to be very demanding. As for Cya taking a while to read, that's only for adding it. Once you are well mixed with a refill thats it. I know it sounds painful, but I would really suggest doing another half drain and refill, before you SLAM. It's your pH you want to worry about, not the TA.
 
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