Help me please with my cya problem

[fireboy1223]

how do i lower the cya in my pool. i keep burning up chlorine.

[superdoopie]

Drain 1/3 of the water and refill with untreated water.

[Cathymac]

We have had problems now for 3 summers with out community pool. I have complained about a "strange" odor and skin irritation along with others but kept getting told there was nothing wrong. I purchased a pool tester kit in June and did a total alkalinity test...after adding over 10 drops of the indicated solution to bring the alkalinity in line I still couldn't correct it. We are paying over $1,000/month plus $500 for chemicals to the same Pool company who took over 3 summers ago. I could not convince the Complex leaders there was a problem but the City shut down the pool one week after I made my plea due to the Cyanuric acid levels. This Pool company charged us $275 to drain and refill the pool. For the first time in 3 years I actually could smell some chlorine in the pool...just the right amount to make it smell fresh and clean. Now, two months later, the City shut down the pool again for the same reason and again we were charged $275 to partially drain and refill the pool. The pool has no leaks and does not require water to be added on a regular basis. I know it is hot and sunny here in Dallas but I think this pool company is ripping us off...if they are testing as I am they should have been aware and solved the problem long before the City had to intercede. What are they doing or not doing and would you find another Pool company? (I had a pool growing up and it was my job to test the chemicals so I know a little about that.)

[chem geek]

The Cyanuric Acid (CYA) level keeps increasing no doubt because stabilized chlorine is being used in the pool. The following are chemical rules of fact independent of concentration of product and 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 7 ppm.

So even with a low 1 ppm FC per day chlorine usage, continued use of only Trichlor as your source of chlorine would increase the CYA by 100 ppm in 6 months if there were no dilution of the water.

Chlorinating liquid or 6% unscented bleach would not increase CYA nor CH. It would increase salt faster, but that's much more innocuous and easier to dilute on a percentage basis. Even at 2 ppm FC per day, after 6 months 576 ppm salt is added compared to half that amount for Trichlor and Dichlor (all forms of chlorine add salt, though not initially, since chlorine becomes chloride when it breaks down from sunlight or oxidizes chemicals in the pool).

There are automatic dosing systems (chemical pumps) or you can consider getting a saltwater chlorine generator (SWG).

[superdoopie]

Its interesting that the pool company who is supposed to be taking care of the pool gets it shut down by the city then charges you to drain and refill. Isn't it their fault the pool was shut down or are you adding chemicals yourself?

[Cathymac]

The Pool Company adds all the chemicals. I can't believe we are being charged for anything at this point. It isn't rocket science is it? When I read the description of CYA on this web site, I thought they may be using stabilized chlorine...they test and clean the pool once a week but told us the problem must be people adding water. That would have diluted the CYA not raised the level...is that correct? Besides, the pool isn't losing water from structural issues, just normal evaporation. The pool was resurfaced and revamped including electrical and mechanical components this last Winter but I suppose they'll blame it on the pool next.

[chem geek]

Evaporation and refill will simply add to the pool whatever is in the fill water -- usually TA and CH. CYA won't leave the pool from evaporation, but will from splash-out, rain overflow, backwashing, but not by that much. CYA only comes from stabilized chlorine sources (of from pure CYA) and is not in fill water. If the CYA level is too high, it has to be their fault and nothing the pool users are doing has anything to do with it. I assume from your description that the pool was shut down due to the CYA level being too high -- what level is considered to be too high in your area -- 100 ppm?

[Cathymac]

I stopped the test at 120 ppm and don't know the City limits but you could smell the CYA from over twenty feet away. Normally I couldn't smell it until I actually got in the water or tested it with a handful of water before going in. It's an odor I have never smelled before in any pool. Several residents who had come down for a swim thought it was a pesticide so they didn't go in the water. Most of us stopped swimming last year because of the skin irritation. Financially, is this a case of scrimping on chemicals or over using them? $500/month seems like a huge sum of money for chemicals even for a pool this size. This pool is used by few people, mostly adults with a poor sense of smell and leather skin! I understand CYA is a stabilizer...what is it's common name? If I just say CYA will they understand which product I am talking about? I want to use the proper terminology when discussing this with the board next week. Thank you all for helping me help my community!

[chem geek]

I don't believe you can smell CYA. I think what you may be smelling are chloramines that form in the pool (especially monochloramine) and that are not getting oxidized fast enough because the FC/CYA ratio is too low (either the CYA is too high or the FC is too low or both). However, your description of a pesticide smell is different than "bad pool smell" normally associated with monochloramine. Skin irritation is also odd and I hadn't heard about high CYA levels causing that either; usually skin irritation is caused by the pH being way off (usually low as is typical in improperly managed pools using Trichlor for chlorine). So I'm at a loss here.

CYA is Cyanuric Acid and is also known as stabilizer or conditioner. However, some forms of chlorine products, called stabilized chlorine, also increase CYA levels when added to water. Specifically, Trichlor (trichloroisocyanuric acid, trichloro-s-triazinetrione) usually comes in slow-dissolving tablets/pucks usually put into floating feeders or inline chlorinators, most commonly 3" in diameter but also available in smaller 1" and 1/2" form. It is very acidic so will lower the pH over time. It also sometimes comes in granular/powder form, though usually advertised as chlorine shock in that case. There is also Dichlor (sodium dichloroisocyanurate, sodium dichloro-s-triazinetrione dihydrate) which is granular/powder and dissolves quickly in water.

Another form of chlorine that does not increase CYA is Cal-Hypo (calcium hypochlorite) usually in granular/powder form, but this increases Calcium Hardness (CH).

The forms of chlorine that do not increase either CYA nor CH are chlorinating liquid or bleach, and lithium hypochlorite (which is a fast-dissolving powder, but VERY expensive).

It sounds to me like maybe this pool service is just using Trichlor pucks/tabs and isn't properly adjusting the pH. This would lead to high CYA levels and low pH which would be irritating and would also produce bad smelling disinfection by-products.

As for chemical costs, I only spend $15 per month on my 16,000 gallon pool (shown here) using 12.5% chlorinating liquid from my pool store I add twice a week plus a small amount of acid added every month or two. However, I have an opaque electric safety cover so my chlorine usage is low at 0.8 to 1 ppm FC per day. Nevertheless, in a typical pool exposed to the sun and with low bather load the chlorine usage is around 2-3 ppm FC per day. So even a 50,000 gallon pool shouldn't cost more than $150 per month in chemicals if properly maintained -- the key is bather load because a heavily used pool can use a lot more chlorine and therefore be a lot more expensive to maintain.

The downside to the hypochlorite sources of chlorine (including chlorinating liquid, bleach and most Cal-Hypo) is that it has to be added every day or two unless you have a pool cover. If you can tolerate wider swings of chlorine level, then these can be added once a week and this is typically done with pool services in hot areas where they have the CYA be 100 ppm and raise the FC to 14 ppm which then drops to around 4 ppm the following week -- your local pool codes may not allow for the FC to be that high (though that is partly because they don't understand the relationship between FC and CYA).

To learn more about maintaining a pool and the terminology used, take a look at the Pool School.

Richard

[superdoopie]

Nice pool, Richard.

Cathy,fire that pool company.

[manistyman]

Hello. New guy here and have registered because I've seen a lot of great knowledge being imparted here. Thank you all.

As for CYA levels being too high, my pool finally went over the top this year after years of puck abuse. I'm in the process of diluting the water in my in-ground plaster pool and my CYA levels are coming down nicely (started today). I've been draining from the bottom of the deep end and adding into the shallow end as well as into the spa (it overflows into the pool).

My question is this: since CYA is heavier than water, would it not be a good idea to let it settle in a calm pool, drain from the bottom, then add to the top? I'm wondering how long it would take for the CYA to settle like this.

Or am I engaged in somewhat wishful thinking?

Any ideas greatly appreciated. Again, many thanks.

Richard 2 (there's a Richard already on the forum, it seems)

[chem geek]

Where do you get idea that CYA is heavier than water? It's like salt that when dissolved in water stays dissolves and well mixed and doesn't settle to the bottom, at least not in something as relatively shallow as a pool. Though you need to dilute the water to remove CYA, removing from the top, from the bottom, from the side, or anywhere else doesn't matter. If you thought that the CYA level differed, then try taking a sample from the bottom vs. the top to see for yourself.

What you are doing is essentially continuous dilution which takes more water to dilute. A partial drain/refill is more efficient, but you need to be careful since some pools should not have their water level dropped too far. In such cases, one can use the sheet or silage bag methods to remove water from under the sheet (or outside the silage bag) and then fill with fresh water above the sheet (or inside the bags).

[czechmate]

To be draining and adding water at the same time is not the best idea.
You dumping part of the brand new water, that you just bought!
Get a sump pump and dump whatever you need, maybe 30%, then add fresh water.
Good stainless pump will cost you about 60 bucks and last you for ever. including your replaster in the future.
You can brush the dust and debris toward it as you pump. and save the filter DE.

[manistyman]

I appreciate the responses with respect to draining and filling, though I am fully aware of the methods used.

As for the "heavier than water" matter, chemgeek, cyanuric acid is heavier than water. I get the idea from basic science. With a specific gravity of 2.5, it's 2.5 times heavier than water (SG = 1.0). I was merely proposing a theory hoping that it might have some validity. For all I know, CYA might stay suspended in water indefinitely, and I did suggest that my theory might be wishful thinking. The tone of your response suggests condescension.

[chem geek]

I am sorry that I sounded condescending and re-reading what I wrote I can see how it sounded that way. The only reason I asked you where you got that idea is that you aren't the first person to bring this up so it's a myth that is propagated by some in the industry. I just wanted to know where you heard it because if it was a pool store then that's one thing but if it's from a manufacturer via a tech. support query, then that's another (and I would call them and follow up on it). In the future, I'll ask it in a different way, such as "Unfortunately, this is not true. Was this information something that came from a pool store or another source?"

The specific gravity you are referring to is for solid CYA. Standard table salt (sodium chloride) has a density that is 2.2 times that of water and sugar (sucrose) has a density that is 1.6 times that of water, but when such substances are added to water they dissolve. Dissolved substances do not settle as their ions or molecules get moved and circulated throughout the solution. There is some effect of gravity similar to that of the atmosphere being denser near the surface, but this effect is only noticeable over much larger distances and only if the water were perfectly still for a very long time. As you said, it was wishful thinking that CYA would be a suspension, but it is not.

Richard