Does winter (midwest) impact CYA levels?

[knarf#2]

This will be my first year closing my AG pool and was wondering if the winter weather will have any impact on my too high CYA of 100? As I have been learning from this forum the best way to reduce CYA is to do a partial drain, but I was wondering if I should do it before closing or in the spring or will the cold midwest winter impact CYA?

Thanks

[duraleigh]

If you let your pool water go South (ignore it) there is apparently a process that, because of the big load of organics in the pool, will eat up most, if not all, of your CYA.

That has never seemed too good an idea to me because you have to clean up a murky pool in the Spring as well as add new CYA. Drain and refill seems a far better choice.

[knarf#2]

My understanding (although being a newbie I could be wrong) is that once we properly close our pools here in the freezing midwest we don't touch them again until spring. I'm sure it's different in NC with your much warmer winters.

So my question is assuming I properly close my AG pool will CYA be signifantly impacted by the winter (reduced from current 100 level)? or will I need to drain and fill to get my CYA down?

Thanks Again

[chem geek]

I believe the process Dave was referring to is that there are certain anaerobic bacteria (that is, bacteria that do not need oxygen to survive) that actually consume CYA. In fact, CYA is considered to be somewhat bio-degradable in the environment (soil) for this reason.

However, if you "properly" close your pool by adding a large amount of chlorine to it, then the bacteria that consume CYA will not survive the chlorine. On the other hand, if you "let your pool water go South" by not adding chlorine to it, then you may get the sort of bacteria in your pool that consume CYA so that when you open up in the spring your CYA levels may be lower (but your pool will likely be full of green algae and need a lot of cleanup). Many users of this forum do seem to startup their pool in the spring looking pretty full of algae and they just shock it to clean it up.

So your options are either to drain and refill (a certain way to reduce CYA) and keep your pool "clean" during closing by adding lots of chlorine, or don't add any chlorine during closing and "hope" that the CYA gets consumed. It's possible that even adding chlorine at the start of closing won't be enough to keep your pool clean as it the chlorine could get consumed over the winter season (this depends on what goes on in your closed pool over the winter).

Richard

[knarf#2]

Got it . Thanks very much for the replies, I think I'll wait until spring to do my drain/refill assuming CYA is still too high.

[Watermom]

However, if you "properly" close your pool by adding a large amount of chlorine to it, then the bacteria that consume CYA will not survive the chlorine. On the other hand, if you "let your pool water go South" by not adding chlorine to it, then you may get the sort of bacteria in your pool that consume CYA so that when you open up in the spring your CYA levels may be lower (but your pool will likely be full of green algae and need a lot of cleanup).


Then there are some of us who do close properly and who open to clear pools, (not green, no algae) and yet still have lost all the cya from their pool over the winter.

[chem geek]

Watermom,

Just curious, but was there a measurable chlorine level when you opened up your pool and found the CYA was gone? Perhaps the chlorine level went away, the bacteria ate the CYA, but it was too cold and not sunny for algae to form???

Richard

[Watermom]

Yes, I always have cl upon opening. This has always been the case for my pool. Always open to clear water.

[chem geek]

Great, another mystery to solve! Namely, how does the CYA go away over a winter closing when there is chlorine in the pool that should prevent bacteria from eating the CYA. Does the CYA breakdown due to the cold? Does this bacteria survive chlorine? Who knows?!

Thanks for the info.

Richard

[geordie]

I second Watermom. I open to clear water and chlorine. However, my CYA level is always significantly lower when I open than it was when I closed. This year I opened and had no measurable CYA at all. The pool is generally closed for 6-7 months out of the year and basically frozen for 3-4 of those months, depending on the winter.

Jean

[chem geek]

OK, I've made some progress in answering this. The PDF file accessed in this link (http://aem.asm.org/cgi/reprint/28/6/1004) describes how the key to degredation of CYA is an absence of dissolved oxygen. Ironically, colder water holds more dissolved oxygen than warmer water so that is counter to what happens in the winter when you close your pool. If the pool is covered, then perhaps oxygen gets used up in the pool. The article refers to chlorinated isocyanurates as sources of CYA so that would mean chlorine would be present and apparently this doesn't stop the degradation process. It seems that this process is catalyzed by biological processes (bacteria, fungi), but that just means it happens more quickly, so perhaps CYA breaks down all the time and that something about winter pools increases this rate.

So, do you both (Jean and watermom) cover your pool? Jean mentioned that the pool would get frozen; how about watermom's pool?

The reason I'd like to figure out exactly how the CYA gets broken down is that it might point a way towards reducing CYA in pools without a drain and refill (or waiting for winter).

Richard

[DerekM]

I am another one who opens with little or no CYA every year. Pool is closed in mid-October with a winter cover, is frozen several months, and, around May 1st, I always open to a clear pool, with little or no Cl and CYA. To reduce maintenance now that swimming days are scarce, I am running out the season with pucks, as I know from experience that whatever CYA I am adding will dissipate over the winter.

- Derek M
PEI Canada

[Watermom]

I usually do cover my pool, however, last fall my cover came off (with a little help from my two golden retrievers, but that is another story!) around the beginning of November. Since the bulk of the leaves had already fallen, I decided to just leave it uncovered the rest of the winter. My water remained clear and pretty clean. Here in south-central WV, my pool doesn't get much ice. Occasionally a glaze, but not a frozen pool by any means.

[chem geek]

Some more detailed technical info is at this link (http://www.pubmedcentral.gov/articlerender.fcgi?artid=91527#B26) which specifies a specific enzyme (cyanuric acid amidohydrolase) that is key to the breakdown of CYA. This enzyme is found in some bacteria (including Pseudomonas and a strain of Escherichia coli; the former is generally hard-to-kill while the latter is easy-to-kill by chlorine). [EDIT] This link (http://taylorandfrancis.metapress.com/(jhkaqtf4ho3eq555y3jk1u45)/app/home/contribution.asp?referrer=parent&backto=issue,1,10;journal,5,25;linkingpublicationr esults,1:103549,1#search=%22cyanuric%20acid%20hydr olysis%22) describes another bacteria (Ralstonia basilensis) found in soil that degrades CYA (there are also fungi in soil that breakdown CYA). It should be noted that the final products of the breakdown of CYA are carbon dioxide and ammonia so if chlorine is also present, then the ammmonia should breakdown to nitrogen gas. [END-EDIT]

Though degradation by bacteria is a clear pathway for reduction of CYA over time, I don't like that since such bacteria shouldn't exist in pools with sufficient chlorine levels and if hearty ones did (such as Pseudomonas), what does that say about our sanitation levels?

I'll keep researching this. As far as using an enzyme to help break down CYA, that is not practical unless one can "turn off" that enzyme by destroying or disabling it after one is through using it.

Richard

[nicole12]

I too properly close my pool and when I open in the spring, I have very little to no CYA and I run high CYA levels due to trichlor. And when I open in the spring, the water is crystal clear. I of course need to shock and get all my levels back up but the water is not green.

[chem geek]

I just received a new CYA test kit (from Taylor) that measures down to 20 ppm CYA instead of 30 ppm that I had previously. At the start of this season, I had just under 20 ppm (perhaps it was 15 ppm) of CYA, but when I measured it today it was way, way less than 20 (not quite clear, but only very slight cloudiness) so it appears that I lost most of of my CYA during the summer. I have a cartridge filter so there is no backwash and we have very little splash-out so the dilution is minimal (and my CH reading didn't go down so there wasn't any sort of general dilution). This didn't seem to affect my chlorine consumption much since I keep the pool covered (electric opaque pool cover) and when it's open for swimming the pool is about 1/3rd to 1/2 covered by shade anyway.

So, I'm thinking that perhaps CYA breaks down all the time though at a very slow rate and it is either most noticeable over the winter or perhaps keeping sun away from the pool ironically makes the CYA break down faster (doesn't make sense, but who knows).

Richard

[NWMNMom]

Just a question, if you have an AG pool, don't you plan on a partial drain to below the skimmer and returns anyways to prevent skimmer/return ice expansion damage? That step right there would lower your startup CYA because you have to add water in the spring....

[chem geek]

My pool is in-ground, but it is true that I dilute it with winter rains and that lowers the CYA level, but I've accounted for that. What I don't understand are the reports of people losing virtually all of their CYA over the winter when they aren't doing a drain/refill. You are right that some people may be doing a partial drain/refill to get below the skimmer in cold climates (it doesn't snow where I live near San Francisco and only sometimes gets to freezing -- the pool water never freezes) and that would lower CYA levels, but people are reporting all of their CYA going away even when they start out with high levels.

I will keep better track of my CYA levels now through next year's summer season and perhaps there is a normal but slow degradation of CYA that occurs and that, for reasons I can't explain (yet), it's either more noticeable over the winter or occurs much more rapidly over the winter. The anaerobic bacteria explanation is real as some of them do consume CYA, but I just don't like the idea of having such bacteria survive in a chlorinated pool.

For now, I'm boosting up my CYA level (since it's nearly gone) and will see what happens over the winter and next summer.

Richard

[NWMNMom]

keep us updated on your findings - is it possible there are "super bacteria" thriving in chlorinated pool environments? Sounds scary but anything is possible these days, especially with the contaminants in our rain/snow......

[Watermom]

Just a question, if you have an AG pool, don't you plan on a partial drain to below the skimmer and returns anyways to prevent skimmer/return ice expansion damage? That step right there would lower your startup CYA because you have to add water in the spring....


Yes - but when you drain below the skimmer and returns, you actually don't throw out all that much water. It would lower your startup CYA level some, but not substantially.

[geordie]

Again, I echo watermom. I do drain below the skimmer but that amount of draining and refilling would not significantly reduce a CYA of 40-50. I've always ***umed there was some dilution of water through the ever increasing small holes in my winter cover. I check the chlorine level and for CYA before I even start raising the water level, because that helps me figure out how many tri-chlor pucks to start with for my CYA. Most often the CYA barely registers (20 or far less) and this year there was absolutely no measurable CYA at all.

For Richard:

Yes I cover the pool, usually in mid-October. And since, by mid-October most of our leaves are IN the pool... that means I have to skim, vacuum and shock before we cover.

Some years our pool freezes solid by Christmas, and other years it doesn't hit that mark until mid-January. Generally it starts to seriously thaw in March, and we usually open in May. Spring of 2005 we had a heat wave and opened in Mid April.

Jean