1st test results - CYA down to ZERO?

[chem geek]

Sounds like a good plan. If you are impatient and want to get your CYA level up faster you can:

1) Put CYA into panty hose and have it hang over the side of your pool over a return. That's PatL's idea and people swear by it. Dissolves in about 24 hours.

2) Buy Instant Pool Water Conditioner by Natural Chemistry which is a slurry of the monosodium salt of CYA. It dissolves quickly in water (unlike regular CYA which takes a long time to dissolve).

3) Add Dichlor to your pool. For every 1 ppm FC you add, you will also add 0.9 ppm CYA. Dichlor quickly disolves in water.

However, your current plan should be fine as even a small amount of CYA protects chlorine from breakdown from sunlight.

As for the CYA going to zero, that is explained earlier in this thread by waterbear where there are anearobic bacteria that consume CYA. This explanation makes sense when the FC level gets to zero. What I have yet to understand is how this happens when the FC does not go too low -- I would hope that this bacteria could not survive in the presence of FC.

Richard

[vanhout]

I wondered the same thing about how this bacteria gets into the pool and survives when there's FC.

At one point, someone said that this is a soilborne bacteria. I do have a mesh safety cover, think the bacteria could get into the pool after closing before the ice comes, when the Cl level has drifted down?

I also would have thought that the winter temperatures here in Michigan would kill this bacteria.

I hoped to be ahead of this for this year, the ice had only melted less than a week before I checked the water, and already zero CYA, zero Cl.

[chem geek]

Winter temps don't kill all bacteria. Many just slow down their metabolism. It's only if the water in their cells freezes over that there would be a problem so bacteria living under the ice could survive. There are even some bacteria that survive in sea ice by secreting their own "anti-freeze" (essentially any high concentration of ions that can fully saturate the water in their cells will do).

It's not the temps that are the mystery so much as the survival with chlorine. The breakdown of cyanuric acid is shown in this link where you have to click on some links to see that the end product is not only carbon dioxide, but ammonia. waterbear mentioned this in another post somewhere. Anyway, so far in my own pool I haven't found any decline in CYA over the winter and I kept the FC level up the whole time. So, at best, we have inconsistent results.

The chlorine level still declines in cold water; it's just slow. In my pool with water temps around 50F and with a pool cover, the chlorine drops barely 1 ppm FC in 2 weeks at a level of around 4 ppm FC. In the summer at water temps of 88F I lose about 1 ppm FC every 2-3 days and that's with an opaque pool cover. If you never added chlorine after your winter closing, I can certainly imagine the level dropping to very low values after several months, especially if there was still some sunlight on the pool.

Richard