Does winter (midwest) impact CYA levels?

[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 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 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 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