CYA stable or going down?

[edwin2014]

Triggered by a remark of chemgeek in post Foam that isn't?
"By the way, don't forget to use Dichlor one day each month to help maintain the CYA level. You might test for the CYA level to be sure it's not too low. Chlorine slowly oxidizes CYA in hot tubs at the rate of roughly 5 ppm per month."

I was wondering if the sticky "How do I use Chlorine in my Spa (or pool)?" would need a remark about degrading CYA?
Until now i was under the assumption that CYA would last the water renuwal periode but now i'm wondering. If i understand it correctly than CYA would go lower in the period of time. So starting at 30 would mean about 25 at the end of the month.
A wise man would say: why not now meassure CYA, and he is so right. BUT in holland the summer is over so it would be very hard to get the optimal sun conditions to do a good CYA measurement
So perhaps next best thing (to keep cover allright) would be to add an amount of stabilizer each month to compensate for CYA loss.
For my spa i guess about 0.3oz (9 gram) of stabilizer (478gallon/FC 4/PH7.5/TA50/CH150/Borate50/temp102)
Or do i miss something?

regards,
edwin

 

[BuckeyeChris]

you could possibly order the 50 PPM CYA reference liquid. Then put together whatever artificial, repeatable light arrangement within your house so that you are reading 50 with the reference vial. Then you can use that same lighting going forward with confidence.

 

[otter86753]

He is in The Netherlands and can't order from TFTestkits unless he has someone get it for him or makes a trip over here. Once your pool water temp reaches below 60 F or 15.5 C, the FC demand will drop and will continue to do as the water temp drops. I hope this helps.

 

[edwin2014]

Will the reference liquid also work for CYA of 30?
Could take it with me next time I'm in the states.

 

[otter86753]

The reference liquid is a test to make sure you can accurately measure CYA using the TF 100 or Taylor K2006 test kit. If you read the reference test at 50, you are doing the test accurately. If not, you need to change something in your test until you accurately read 50 eg. light, distance, mixing etc.

 

[chem geek]

Yes, the sticky should refer to dosing with Dichlor about one day per month (about 6 ppm FC worth). While testing for CYA would be ideal, just adding Dichlor one day per month should be OK since the degradation rate is fairly slow.

 

[edwin2014]

not sure which dichlor i need. For CYA add's i use the Pool Stabilizer from melpool. So i guess i'm somewher in the ball park if i add 0.3oz (9 gram) each month until the bright sun return's.

 

[chem geek]

Sure, you can use Pool Stabilizer if you want. You don't need to use Dichlor. You want to add around 5 ppm CYA per month though after a couple of months you can test the CYA to see if you are indeed losing around 5 ppm per month. So yes, 9 grams (0.32 ounces weight) in 478 gallons would be 5 ppm CYA.