Does CYA 'degrade' at any sort of average rate?

[aquarium]

I know CYA can be lost to splash-out and drain-off, but does it -ever- go away all by itself just due to environmental conditions?

The reason I ask is that I'd like to run my pool low on CYA (20ppm or so) and just barely crack open my auto-chlor with the 3" trichlor pucks inside while using bleach for most of the chlorine.

I now know how much CYA each puck is adding, but I don't know how much is going away by itself, if any.

Thanks,

TW

[Watermom]

In some pools, no, it doesn't go away. Other people, myself included, find upon opening each spring that it has all disappeared. I open to a clear pool each year with no CC, so it is quite a mystery.

[waterbear]

No mystery at all, the cya has been biodegraded by anerobic bateria to ammonia compounds and urea.

[halds]

If ammonia conversion were happening, wouldn't you register a high CC level?

[ivyleager]

My CYA was 100ppm at the end of last season, and is still @ 100ppm. I haven't lost any. Been using bleach exclusively since last year. I am considering deliberate algae mess at end of this season to see if that will degrade any CYA.

CaryB
Go 'Canes!!!

[Watermom]

If ammonia conversion were happening, wouldn't you register a high CC level?

According to Ben -- yes. That is why I said it is a mystery. I always open to a clear pool, no CC, no cya.

[Watermom]

My CYA was 100ppm at the end of last season, and is still @ 100ppm. I haven't lost any. Been using bleach exclusively since last year. I am considering deliberate algae mess at end of this season to see if that will degrade any CYA.

CaryB
Go 'Canes!!!

Instead of a deliberate algae mess, why don't you just do a partial drain? If you drain half the water, that would put your cya down to about 50 which would be a good level.

[waterbear]

According to Ben -- yes. That is why I said it is a mystery. I always open to a clear pool, no CC, no cya.

In a complete denitrification the reaction will proceed all the way to nitrogen gas which will leave the water. This ususally does not seem to occur in pools but is certainly possible. This anoerbic dinitrification is used in aquariums successfuly with dinitrification filters that control the process so it always proceeds to nitrogen gas. However if they malfunction they produce a LOT of ammoinia which then can kill the livestock in the tank. I suspect in most pools the conditions just aren't right for the process to procede all the way. It is not algae that cause the denitrification. Algae is aerobic (needs oxygen) There are several speicies of anerobic bacteria that are ususally found in soil and in sedemint in ponds, lakes, and oceans that do the denitrification. They need still or VERY SLOWLY moving water (pool pump off), darkness (cover on pool), and no oxygen (consumed by any algae growth, most likely, and once again, no water circulaton) for the process to go to completion and usually a source of sugars or alcohols for food to speed the process up. I suspect the latter is what is missing in most closed pools that exhibit anoerbic denitrification.

[p.p.h.]

I lost 40ppm CYA in a matter of months after my initial fill in late March. I've backwashed probably about 5 times and now we got alot of swimmers but 40 ppm lost is alot, thats half my pool drained!!! Same test kit used for initial test and the recent tests.

[Henrys514]

So, cleaning off the cartridge filter can make it go away too? The instructions always said to avoid cleaning the filter for 3-5 days after adding the CYA to the pool. I figured by then it would be in your system enough that additional filter cleanings wouldn't make that much of a difference to the ppm.

No wonder we have such a hard time holding stabilizer. Our pool gets a lot of junk in it, so we have to clean the filter quite a bit. We're at 35ppm now, but I just washed the filter yesterday. Is it a good idea to check the CYA after cleaning/backwashing the filter?