Off the charts CYA

[jgold723]

My newly purchased Taylor K-2000 tells me my CYA is ... well, I don't really know because it's off the chart in the comparator tube. Well above the 100 ppm mark. Which makes sense given that my FC has always run very high (today it's 14.5 ppm according to this morning's test) and I've had an ongoing issue with algae.

Reading here I see my only solutions seem to be a water replacement or osmosis. I have a vinyl, inground pool (16 x 32). I can't just drain and refill as that will ruin my liner. Is there another method of accomplishing this?

And, since the idea of replacing that much water gives me hives (we have high water rates here), what are the long-term consequences of the high CYA? Other than the recurring algae issue, I've never noticed any serious issues with the pool.

 

[Mr Bruce]

You are correct that a complete drain could ruin your liner. You can drain to 1 foot left in the shallow end. If you didn't want to drain at all, you could put a sump pump in the deep end and a hose in a bucket on the steps and exchange water. Unless you can exactly match the drain/refill rate (unlikely) you'll have to keep an eye on it.

Without proper FC for your CYA not only are you prone to algae but the water is potentially unsanitary. (If algae can grow what else might be growing?)

 

[Donldson]

In order to assure the water is sanitary you must keep your FC levels above the Minimum FC per this chart: FC/CYA Levels. These numbers can be extrapolated, but you need to find out your actual CYA number to manage it. Because of the way the test works you can't really guess what your CYA level is if it is over 100, you would need to run a diluted test where you mix 1/2 tap water and 1/2 pool water and use that to perform the test, then multiply by 2.

Let's say your CYA is 200 for instance. In that case you would need to never allow your FC to drop below 16, and you would want to keep it around 20-25. While this would be perfectly safe to swim in it would prevent you from being able to run your pH test. It can be done, just wouldn't recommend it. Since you have algae it is going to take the SLAM Process to correct. That would require bringing your FC up to 80 (if your CYA is 200) and keeping it there for a while while testing at least twice a day, preferably 5-6. You'll want to get some FAS-DPD refills, it's going to take a lot to measure chlorine that high if it even can.

High water prices or not, this problem isn't going away. If you are still feeding your pool tablets it is actually getting worse every day. This only has to be a 1-time procedure. Change the water, eat the bill, and pull the tablets out and you won't ever have to deal with this again. Trying to live with this problem is going to be a lot more painful than fixing it.

 

[Richard320]

The operative words are, "I've had an ongoing issue with algae."

Yes, it' s possible to maintain a pool with super-high CYA. I've done it. Clearing a pool with super-high CYA is pretty much impossible. About the best you could hope for is less-disgusting.

What you consider high FC isn't even close to maintenance levels. There is no test kit that can measure FC at the levels you'd need. The amount of bleach you'd have to add would cause your pool to overflow.

chloroxtanker.jpg

• Richard320
• Apr 11, 2019

Your water costs will not even approach the bleach costs if you try to clear your pool without water replacement.

 

[tim5055]

Richard is correct. I also have maintained a pool with 250+ CYA. But, it was clear, I had no algae and I was able to lower the CYA gradually.

JD is also correct, you must maintain your FC at the correct level for the CYA in the water to have sanitary conditions.

 

[jgold723]

Thanks for the replies -- that's about what I expected to hear, but wanted to check. Question about the trichlor tabs though -- what's my alternative if they are causing such a huge problem? These seem to be the go to standard for chlorine pool sanitation.

 

[setsailsoon]

Thanks for the replies -- that's about what I expected to hear, but wanted to check. Question about the trichlor tabs though -- what's my alternative if they are causing such a huge problem? These seem to be the go to standard for chlorine pool sanitation.

JG,

Thanks for your posts and candid questions. The reality is trichlor is only the standard for people that are ill-informed about the way CYA interferes with disinfection or they chose to use trichlor knowing that they must control CYA build-up via water replacement. I know several people in the latter category, there's nothing wrong with this approach. My brother uses this approach, and he's diligent about it because he knows it's critical to drain/replace for proper disinfection. Unfortunately many do not do this. I personally much prefer TFP methods because I believe it's more effective and practical to use liquid or SWG. If you dig into the industry literature you'll find that even the manufacturers of trichlor are starting to acknowledge the impact of CYA on proper disinfection. Why? My guess is that like many other chemical manufacturing companies, they are now recognizing the liability of not disclosing this. I believe pool stores are complicit in the continued misinformation by often failing to inform their customers properly. They could also be conflicted by the fact they sell the trichlor and chemicals to "fix" inevitable algae blooms if CYA isn't drained down properly.

I hope this is helpful and good luck to you.

Chris

 

[duraleigh]

I looked at the water rates for the town you listed and, if I read it right, it would cost you about $65.00 to drain your pool completely. Perhaps you should call your municipality and see what the charge is.

You may well get by by only draining half.