Cya=20.

[morzh]

After opening the pool this Monday I just got to the balancing. The usual, have to bring the TA to 120 from 60 etc.
But I noticed my CYA (as measured with he TF kit) is about 20.
The FC after adding a gallon of 10% stuff (and the bottle was bought last fall) this morning is 6ppm witw 0.5 ppm CC.
Anywho, CYA after being well over 100 two years ago dropped to about 50-60 last opening of 2017 and is now 20.
Q: I was struggling with it and praying it falls off; now that it is that low, do I want it up?
If yes, I bought some Cl tabs like 3years ago, that still are good (judging by smell) and contain CYA, and I have not been using them for this very reason - did not want CYA to go up. Is this a good way to bring it up? And how much will it be going up per tab? (20K gallon pool)?

Mike

 

[mknauss]

PoolMath. Effect of Adding Chemicals.

No need to mess with TA. If you use pucks your pH will be held down and your TA will drop.

No surprise the CYA drops. It naturally degrades 3-5 ppm per month, depending on UV impact and chlorine levels.

 

[SpaceCoast]

I thought CYA never degrades and the pool has to be drained to remove it?

 

[mknauss]

Nope. Just does it slowly.

In some places, especially were the pool is closed for winter, bacteria can enter the pool water and consume the CYA. That creates ammonia. Which takes enormous amounts of chlorine to clear.

 

[borjis]

It sounds like you had a rare cya eating bacteria total conversion. instead of converting and leaving ammonia, the cycle completed and went to nitrogen.

Great, now you can set your CYA at a more manageable 30-50 ppm.

Not sure why you would want your TA at 120, that's pretty high. 60-80 seems to be the most common, best for that.


EDIT: I forgot to add, make sure you test cya with your pool water around 70 degrees / room temp (at least).

If it's mid 60s or less, you will get a false low reading.

 

[morzh]

MknaussN

No ammonia. At least no smell of it, not look last year, not this.
I don't use pucks, I use bleach. I was considering using them tobring up CYA.


Borjis

The water to the touch is in mid 70s.
As for the TA, everywhere I go it says 80-120. 60 I guess is not too bad but is outside of what everyone seems to recommend.

 

[DeanP66]

Try leaving your TA at 60 and see how that affects your pH rise. I bet it will be pretty steady and only go up very slowly, unless you're using pucks which are acidic and tend to keep the pH low. Also, it's always nice to know the pH, TA, and CH of your fill water. My TA tends to climb because my fill water has a TA of 220. So, I keep that in mind when I'm balancing my chemicals. My CH was 300 from my fill water which made my overall CH rise somewhat faster than I liked, so I ended up using soft water to refill my pool for top ups. Its CH is only 30 so my CH should stay put for quite a while now. That's why it's important to know your fill water numbers.

 

[morzh]

I decided to use pucks as right now they seem to be a good fit for the situation plus will justify the old expense sonewhat.
I will add some of the pH-UP I have from a couple of years back to raise pH from 7.2 it is at now and see if it rises. If not I'll raise TA just a bit.
The FC as of this morning is the same as it was yesterday so CYA is probably doing some job.

Tonight is the first splash nght! My kids have been clamoring for it since May.