Quote Originally Posted by btozzo View Post
Hello All:

I thought I'd post a new thread for this one. It looks like my "Chlorine Lock" is over thanks to all of you. Also, following your advice I ordered and received my Taylor k-2006 test kit and love it. I'd like it if someone could do a little hand holding for me as I don;t want to screw up and I'm not exactly full of confidence yet. Here are my vitals according to my new kit:

1. Free Chlorine 1.6 ppm
2. Combined Chlorine 0.4 ppm
Use the 10 ml size sample instead of the 25 ml size. A test resolution of .5 ppm is more than enough and you will save on reagents!
3. pH 7.4
4. Alkalinity 180
5. CYA < 30 ( I could see the black dot when it was completely full!)
6. Calcium Hardness 220
16 x 36 24000 vinyl in-ground with Hayward EC 65, 1 skimmer and 3 returns

My first questions is that I am backwashing and adding DE and my circulation is slowing down and pressure up to about 24 pretty quickly. When I backwash my pressure drops to around 12. Can this be due to my CYA?
No, nothing to do with CYA directly but if you have low CYA and a lot of sun you might be dealing with nascent algae blooms. How much DE are you putting in when you recharge after backwashing and how much DE does your filter take? (I am not a big fan of backwashing DE filters but feel they should be broken down and then recharged when they need cleaning. You never really know how much DE you are backwashing out and it is very possible to over or undercharge them after a backwash.) Is your water cloudy or clear? If you have cloudy water then it just means the filter is doing what it is supposed to anc filtering out stuff
I seem to remember something about that in the Taylor book.
reread the book
Second, I believe my CYA and my alkalinity are connected. How much of what should I add to get my CYA up a little?
CYA does add to total alkalinity but not to the buffering effects of the bicarbonate in the water. Taylor says that the contribution by CYA should be ignored and give a formula for corrected TA. However, the contribution to TA by CYA is about 1/3 the CYA reading at a pH above about 7.4 and and about 1/4 the CYA reading below that so, unless you CYA is extremely high (say in the neighborhood of 100 ppm) it really is not going to make any appreciable difference and can be ignored. In your case, with a CYA of less than 30 ppm the difference between uncorrected and corrected TA readings is smaller than the precision the TA test is capable of!
Thanks everyone,

Bill
To raise your CYA you add CYA (cyanuric acid, commmonly called stabilizer or conditioner at the pool store). In a 24000 gal pool every pound (16 oz by weight) of CYA will raise the level by about 5 ppm. I would pour 2 lbs. SLOWLY into your skimmer with the pump running, run the pump 24 hours then switch back to your normal run time, do not clean the filter for a week and then retest the CYA. Repeat as needed to get into the 30-50 ppm range.