CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun Daily

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jgellatly002

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Jul 2, 2012
11
I have a 30,000 gallon vinyl-lined in-ground pool that sits in direct sunlight for at least 10 hours daily. As a result of using tri-clor tabs and a di-clor "shock" product (as recommended by my inherited pool guy) my CYA levels have increased to over 150ppm (currently, my free and total chlorine levels are approximately 10ppm). From what I have read, ideal CYA levels are typically in the 50ppm range.

I have recently been dealing with algae, which I had not had for the first month of the summer. With a FC level exceeding 10ppm, I was thinking I may have a chlorine resistant algae issue. However, I am thinking my chlorine may be ineffective given the astronomical level of stabilizer in the pool.

My primary concern is to combat the algae problem. However, I'm not sure I can buy enough bleach to do this with such a high CYA level. My first reaction is to drain some of the pool water, refill, test the CYA, and then dump some liquid chlorine bleach into the pool. Was hoping for some advice as to what an appropriate CYA level might be for a pool that sees this much direct sunlight.
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

Welcome to TFP!

You need to bring down your CYA level to something more reasonable (below 80, preferably around 50), or you are going to have a rough time of it. Higher CYA levels make chlorine progressively less effective, so you need to use higher FC levels to compensate. When CYA gets too high, the required FC levels become so high as to be impractical and to bring up numerous secondary problems.

The most practical way to lower CYA is to replace water.

You also want to look at what chemicals you are using that raised the CYA level up that high to begin with, and reconsider their use.
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

jgellatly002:

Definitely need to lower CYA to around 50 or so. Your life will get much easier.

Not sure where you are located, but my pool is in the full Texas sun for 10+ hours. My current CYA is 30. On a sunny day with seasonal temps in the mid-upper 90's, I lose about 2 - 2.5 FC / day. Several days last week we got above 100. On those sunny days, I lost between 2.5 and 3 ppm FC / day. I manage my FC level within the target range (2-6 ppm per Pool Calculator) for my CYA. I add chlorine (bleach) each evening based on the next day's anticipated weather conditions to make sure that I remain within my target range given the expected FC loss the following day.

I will keep monitoring my FC levels daily and will add more stabilizer if needed. I prefer to run at as low a CYA level as is practical for my pool because, as Jason stated, the only practical way to lower CYA is to replace water (a task we want to keep to a minimum in Texas).
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

Hello...
I have similar circumstances with my pool. 10* hours a day of direct sunlight here in sunny South Florida. I maintain my CYA levels around 35-40 ppm...mostly because we get TONS of rain down here (thank you Tropical Storm Debby) and its easier to shock my pool with lower CYA. However, that also means that I have to be more vigilant in watching my FC levels. I work at night, so when I get home around 1am ish, I test my FC. My pump runs twice a day....6 hours during the hottest time of the day and 6 hours at night (so I can add chemicals).
Right now my avg water temp during the day is 88-90 degrees...bleh. :grrrr: But its still cooler than the avg air temp. :lol: I keep my pH low...about 7.2 so that my chlorine works more efficiently as well.
I also like to keep lower CYA levels because sometimes my mom takes care of the house and pups while I'm out of town and low CYA levels make it easy for me to toss a few pucks in the floaty duck and not worry about explaining how to manage my pool as well as when to feed the dogs, etc etc.
So the answer to your question is...your ideal CYA level depending on multiple factors.
1. do you need to shock often because of excessive rain, swimming dogs, landscaping, etc.
2. how much time do you have to test your FC everyday and make adjustments?
3. do you have the need to use those God awful (but sometimes necessary) pucks?
There are many other factors to consider...but these are the ones that affect me the most and why I keep a lower CYA even though my pool gets TONS of sun. On average I lose about 2-3ppm a day during the hottest months, which is easy to replace when I get home from work at night.
50ppm or higher may work just fine for you...experiment a little starting with a lower CYA and see when the balance kicks in. I was in your situation when I started with this pool...I drained more than half the pool to lower my CYA and still was high. Weeks of vacuuming to waste finally helped me get it under control and I've always sworn NEVER again! LOL..
Good luck...hope i helped!
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

Thanks. I'm still so surprised my CYA level got so high. It was hovering around 80ppm all throughout June and I was losing FC on a regular basis so I assumed the 80 level was fine. Then I dumped the recommended doseage of the Anthony Sylvan brand Super Pool Treat into the pool and BAM! CYA off the charts (this was last weekend). In the matter of a few days I managed to have an algae bloom. I'm scrubbing and vacuuming incessantly so as not to have a full blown swamp in the backyard but what a pain!

I'm currently draining a good portion of my pool (can't wait to see my water bill). I was curious as to how I was maintaining a FC level exceeding 10ppm even with all the rain and sun but I suppose it makes sense I wouldn't lose that much chlorine with such a high CYA level. Hoping I can get the level down to at least a manageable level (at least below 100) by draining a few thousand gallons and then refilling. Then I'll dump plain ol' bleach into the pool to try and kill the algae.

And yes - NEVER AGAIN with these Dang pool chemicals. NEVER!!!
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

Good luck! Let us know how it turns out or yell with questions....There are so mamy knowledgable people who check this website daily that you're sure to get a quick response. Everyone here really saved me lots of time and money!!
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

You are going to have to do more than just a few thousand gallons to get that CYA back down!

I hear you on the water bills, my last bill was over 50,000 gallons. I had one month over 150,000 gallons last year! 75,000 during the summer isn't uncommon for me. :(
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

I agree with Robbie H. You're gonna HAVE to drain at least half of your pool if you want to halve the CYA level. Go to the pool calculator and find the CYA section. You can type in what you want your "goal" CYA level to be and it will tell you how much you need to drain. I would do half the pool volume to jumpstart it and then vacuum to waste weekly, replacing the water you remove which will slowly bring you back into the norm! But you've GOTTA get that under control. The expense of the chlorine you save will help offset the expense of the water replacement...and reduce your headaches! Bite the bullet on this one and drain! sorry :cry:
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

And stay away from A&S Super Pool Treat. That's Di-Chlor, aka the fastest way to raise your CYA--short-term it is even faster than pure CYA because it dissolves faster. You get roughly .9ppm of CYA for every 1.0 ppm FC with that stuff. Not recommended for anybody with high CYA.
 

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Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

I believe A&S is just rebranding from N.Jonas and the Super Pool Treat MSDS shows it is just Dichlor. The following are chemical facts independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

With 150 ppm CYA, an FC below 11 ppm can develop algae growth. Unless you are using a Taylor K-2006 or TFTestkits TF-100 test kit, I wouldn't necessarily trust your FC and CYA readings (especially if you are using test strips or pool store measurements).
 
Re: CYA / Chlorine Levels for Pool w. 10+ Hours Direct Sun D

After draining more than 50% of my pool water, I refilled and let the pump run for 24 hours without adding any chemicals. Coincidentally, I received my new TF-100 testkit. According the the TF-100, I was able to lower my CYA to approximately 80/90ppm. While this is a tad on the high side, I'm going to attempt to ride out the summer at this level, hoping for dilution through splash-out/operation and refill throughout the summer. Using Clorox as my chlorine source, I've been able to maintain FC around 13ppm (TC 0ppm), which seems like it is the appropriate level given my CYA level.

I shocked the ever loving Crud out of my pool for a few days and was able to cure my algae problem with a major dose of chlorine. The water cleared in approximately 2 days with the filter running 24 hours per day. So nice to have a sparkling pool again.

Never with the pool store chemical products again.
 
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