CYA seems to be 0

[JasonLion]

16 oz of cyanuric acid/stabilizer will raise CYA by 7.5 in 16K gallons. Even four pounds would only raise CYA by 22, which could still test as below 20. The CYA test isn't all that precise, it can be off by enough so that a CYA level of 22 can sometimes show up as below 20.

 

[josemary9]

My TA is around 80, this is a bit low isnt it? The pH is remaining pretty steady at 7.5. So do I leave CYA on its own or get more stabilizer?

 

[JasonLion]

TA and PH interact, but have nothing to do with CYA.

TA at 80 is just fine unless you are using trichlor tablets (in which case it is low). As long as your PH is stable, leave TA alone.

I recommend raising CYA up to around 40 to 50.

 

[josemary9]

What purpose does CYA serve? If chlorine lasts longer with low CYA, why raise it?
I do have some trichlor pucks I am using up, mainly when we are away to maintain the chlorine, so raise TA?

 

[JasonLion]

CYA protects chlorine from sunlight. The higher the CYA level, the less chlorine you lose each day to sunlight. The counter point is that CYA buffers chlorine, reducing the level of active chlorine in the water. To compensate, you need to raise the FC level, to keep the level of active chlorine the same. Even though you are raising the FC level along with the CYA level, you still save on chlorine lost to sunlight. Other effects start to cause problems when CYA levels get too high.