Drain/Refilled - CYA didn't go down - now what?

[sdaggie]

I drained and refilled 40% of my pool to reduce my extremely high CYA, alkalinity and chlorine. However, my CYA did not go down that I can tell! What is my next step?

NEW NUMBERS
FC = 9
CC = .4
PH 7.8
Calc = 210
TA = 325
CYA = 150 - 'Guesstimate' because black dot disappears so quickly.

I've learned so much about pool chemistry and the methods suggested here but I am frustrated the CYA didn't go down! Thank you for your suggestions!

 

[duraleigh]

Re: Drain/Refilled - New Numbers - now what?

About the only thing you can do is drain again. The pool is virtually unmanageable with a CYA of 150.

 

[sdaggie]

Re: Drain/Refilled - New Numbers - now what?

Does it make sense that it did not go down after the drain?

 

[heugeneo]

It probably did go down, but your cya was higher than the 150 to begin with. You need to do a dilution test to get a better guess at your actual cya. Dilute 1 part tap water with 1 part pool water and redo the test. Multiply the result by 2. If the dot disappears before you get to the 100 mark, then dilute 2:1 and multiply results by 3. You can keep diluting until you get a decent reading. I had to dilute mine 10:1 initially and learned my cya was about 500!

 

[DaninFLA]

your CYA was higher before is all. you said 150, did you do that by dilution? the higher the CYA, the larger the margin of error on the test. I believe I read that it is plus or minus 20ppm when you are at the upper limits of the test (100ppm). when you do a 50/50 dilution test, the margin of error goes even higher, probably 30.

you need to keep emptying your pool and refilling until you get the CYA test results within range. larger water changes are better than multiple smaller ones if you have a deep water table. I would do 70% by default if you have a very deep water table and are able to do it. one 70% change is going to cost less time and money than multiple small refills. if you did two more 40% water changes, the net reduction in your CYA would be 64% and you would have used 24,000 gallons of water. a single 70% water change would lower your CYA by 70% and you used 21,000 gallons. so you can see how much more efficient that is

I would do the larger drain/refill and then retest and see whats needed

 

[DesertPete]

Had the same experience. 3 Partial drains and still high CYA. Tried Bioactive twice and no better. So I finally drained the pool.

 

[ping]

When you replaced 40% of the water, 40% of the CYA was removed. You can't measure that difference because the CYA is extremely high and the test only reads to 100. The CYA test is logarithmic, so any reading above 100 can be way over 100 such as it is in your case.

The best option for you is for you to continue draining and refilling until the CYA hits 50 or less. Don't drain all at once with the vinyl liner.

 

[Donldson]

CYA = 150 - 'Guesstimate' because black dot disappears so quickly.

By your description I would say it is far more likely your CYA is easily a couple hundred and was several hundred before your water change. I would do another 40% if you can, there is little risk of overshooting it at this point.

BTW, I hope that some new people see what the pool store has gotten you in to between this and your TA. Not that it was your fault, you had no reason to believe they were steering you wrong, but what a mess.

 

[DesertPete]

Thank you for the pool store comment.

 

[sdaggie]

I just completed my second partial drain and refill due to sky high CYA and TA. Here are my new numbers:

FC = .4
CC = .4
PH = 8
TA = 320
CH = 225
CYA = 72

The water has a greenish tint to it after refill. What should I address first - PH or chlorine?

Thank you for your advice - I am new to this method but I have to admit, throwing in a bunch of shock is looking very easy right now - but I am trying to stay strong

 

[poolnoob.ca]

Sdaggie, throwing in a bunch of shock is a pool store technique, and what likely got you in this mess in the first place. You just may be adding lots of chlorine in the near future, but i suggest doing it in a controlled scientific method, the SLAM.

As for addressing pH and chlorine, you can address them both today, 1/2 hour apart. Use pool math to get pH to 7.2 in preparation to SLAM, and get chlorine up to 8ppm with bleach or liquid chlorine as your CYA is about 70

 

[sbcpool]

Re: 2nd Drain/Refill - New Numbers

Chlorine. In comparison pH is a minor concern. Make sure you add enough chlorine for your current CYA.

How are you getting such exact numbers for your CYA?

 

[sdaggie]

Re: 2nd Drain/Refill - New Numbers

@sbcpool - I had to do the alternate CYA test with partial tap water and multiplied by 2 to get 72.

 

[Donldson]

Re: 2nd Drain/Refill - New Numbers

@sbcpool - I had to do the alternate CYA test with partial tap water and multiplied by 2 to get 72.

If your CYA is below 100 then you don't need to dilute the test, in fact doing so causes a higher margin of error. Redoing the test without dilution will give you a more accurate reading.

Assuming your CYA is around 70 or 80 then you can start a SLAM if you want, but it will take a decent amount of chlorine to get your FC high enough. It would be better to bring it down a bit more, but that's your call. If you are really chomping at the bit and are willing to use some extra chlorine then you can begin. Be sure to bring your pH down before starting.