CYA at 70 - draining and don't want to again

[frank6]

When I opened the pool I adjusted the ph and alkalinity with baking soda and soda ash, I was getting no clorine level at all (even after adding lots of 3" pucks to my automatic chlorinator and floater, and adding a few gallons of bleach), so I was told to test the cyanuric acid. It is about 70. I know that I have to dump water and add fresh to correct the problem, but I want to make sure this does not happen again. Am I using the wrong chlorine and is there something else I should be using? Also, is it safe to swim in the meantime? I have a 15x30 above ground pool with a DE filter. My ph is about 7.4 and my alkalinity is about 90. My chlorine does not even register on my test kit (from Leslie's - dpd test kit). The water is crystal clear.

Thanks for any help you can give me.
Frank

[rbonin]

According to the "best guess" CYA chart, at 70ppm CYA, you need to maintain at least 5ppm of free chlorine in order to properly sanitize your pool:

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

Your problem is those pucks that contain stabilizer - it keeps building up in the pool. To avoid the problem only use unstabilized chlorine (such as plain unscented bleach) and add CYA separately as needed (once a season probably). I don't understand why you are getting no Cl reading with your high level of CYA it should not be burning off by the sun. Hopefully others will have some ideas on this.

~Rick~

[frank6]

Ok, I just tested everything again and these are my current readings after I stopped using the pucks for a few days:

Ph 7.2
CYA 50
Alk 80
Calcium 70
Bromine 0
Total Cl 1
Free Cl 0

How much regular bleach should I be adding? Maybe I'm just not putting enough in. Thanks again...

[CarlD]

Ok, I just tested everything again and these are my current readings after I stopped using the pucks for a few days:

Ph 7.2
CYA 50
Alk 80
Calcium 70
Bromine 0
Total Cl 1
Free Cl 0


How much regular bleach should I be adding? Maybe I'm just not putting enough in. Thanks again...

Figure 12,000 gallons. 1 gallon of regular bleach will add 4 1/3 ppm of FC. 1 gallon of Ultra Bleach will add 5 ppm of FC.

You need to shock to 15ppm first--that's 3 gal of ultra.

then you need to keep a regular FC of 3 to 6 ppm for your CYA of 50. If FC is 0 or 1, then 1 gallon of either bleach will do it.