CYA test help...Am I doing it wrong?

[NannyAng]

I have the HTH 6 way test kit from Walmart...

I test Cl and pH every morning. Cl is sually at a good 2ppm, but if I'm going to have 2 or 3 toddlers swimming that day, I re test to make sure there's enough chlorine to kill any accidents they may have. On many such occasions my Cl level has dropped to almost zero after only 4 or 5 hours. I tried testing the CYA level to make sure my water was stable and not breaking down the chlorine too fast. The instructions say that the water should turn cloudy after mixing in the test chemical, but I'm not getting that result, it stays clear. What am I doing wrong?

[robbym70]

I have the Taylor2006 test kit and the method may be different but using that set if the water is clear after mixing the chemicals together the CYA is considered to be below 30. Could this be the case for the HTH kit? Not sure but I bet it is similar meaning you have CYA level below 30.

[Watermom]

Yes. If the water doesn't turn cloudy, then your CYA level is less than 30 which explains why you can't keep chlorine in the pool for a full day. You should try bumping it up to around 50ppm.

What is the volume of your pool? What are you using as your source of chlorine?

[NannyAng]

Volume is slightly above 1000 gallons. I've been using 7.86% bleach but just got my shipment of dichlor shock, so I'll start using that tonight.

[NannyAng]

I started using the dichlor shock last night. My pH has remained at approximately 7.8-7.9 for the 2 weeks I've using only liquid bleach, but I noticed it finally dropped to 7.5 today. I know that dichlor has some stablizer in it, so that should begin to increase my CYA level shouldn't it? If so, how long do you think it should take to raise my CYA level high enough to show on a test?

[BigDave]

How much dichlor have you used?

[NannyAng]

For the past 3 days, I've been adding approximately 1 ounce (2 tablespoons) every night plus another 1/2 ounce mid day before the kids swim. So a total of approximately 6 ounces so far.

[singingpond]

Not sure if you saw my response, in your other thread on the same topic:

http://www.poolforum.com/pf2/showthr...A-testing-help

I'll repeat the relevant comments (in case the other thread disappears):

I believe that the ratio of ingredients in dichlor is such that for every 10 ppm FC (free chlorine) you add (via dichlor), you also add 9 ppm CYA. The free chlorine gets used up on an ongoing basis, one way or another, but the CYA remains in the water. If you know how much dichlor you've put in, it should be possible to estimate your current CYA level, and also to estimate how much total dichlor you'd have to put in to reach 30+ ppm of CYA. Looking at it another way, to reach 30 ppm of CYA, you'd have to put in enough dichlor (total) for about 35 ppm FC. If you look at poolcalculator.com (putting in 1000 gallons for pool volume) and ask for FC to go from 0 up to 35, that seems to call for about 8 oz. total of dichlor. I think that's in the ballpark anyway (I'm new here on the forum, so take these estimates with a grain of salt accordingly).

[BigDave]

6 oz. dichlor will add about 23 ppm CYA to 1000 gallons. It'll take another two oz. before it can be measured.