CYA question

[mikemedic]

Ok, I am using the BBB method as well as some Trichlor pucks. I have better luck holding the FC with higher CYA.
My CYA was 40 before and using about 4 PPM a day of FC.

My PH was getting high and I wanted to bump up the CYA a little so I used the Trichlor pucks to accomplish. I used 15 3 '' tablets and I was under the impression that each had .6 ppm of cya in them hence 15*.6 is about 9 ppm of cya added.
I just tested and my CYA is like 70-75. I tested a few times before and know the cya was about 40. Any body want to take a stab at that?

Is there something else that will throw off the CYA test?

[chem geek]

The rule is that for every 1 ppm FC introduced by Trichlor you get 0.6 ppm CYA. It is NOT that one 3" tablet/puck gives you 0.6 ppm CYA. The amount of CYA and FC you get from a puck depends on the size of your pool. Also, puck size (height) varies a bit with pucks ranging from 6 to 8 ounces weight.

Assuming an 8-ounce 3" puck, then in 10,000 gallons of water one puck will add 5.5 ppm FC and 3.3 ppm CYA.

In your case, 15 pucks added 30-35 ppm CYA so the size of your pool is about (10,000 gallons)*(15 pucks)*(3.3 ppm CYA per puck)/(32 measured CYA) = 15,470 gallons.

Richard

[mikemedic]

Ok, thanks
I will back off on the pucks and use BBB and monitor.
Thanks
Mike

[mikemedic]

Ok,
My pool is about 22,000 gallons as best I can estimate.

How much CYA would you guess is added to my pool for every 3 "" tablet?

So 3.3 ppm CYA per tablet per 10,000 gallons as an estimate. If I am roughly twice that then every puck would be ~1.7 ppm cya.

When I measured the 40 PPM cya I have added water a few times and backwashed and had some heaver rain so it diluted a little. I was planning on using a few trichlor pucks on while on vacation so I didnt have to depend on stepson to add bleach every night. I dont want to go over board with cya though.

Mike

[chem geek]

If each 3" tablet is 8 ounces, then in 22,000 gallons that's 2.5 ppm FC and 1.5 ppm CYA. If each tablet is 7 ounces, then it's 2.2 ppm FC and 1.3 ppm CYA. If each tablet is 6 ounces, then it's 1.9 ppm FC and 1.1 ppm CYA.

Richard