Chlorine Lock ?

[Big Splash]

You have the right idea. You can drain down as much as leaving a foot of water in the shallow end and you should be ok. I would guess you need to do 3x to get close to 50 cya. That is... if each drain equals 25% of your total pool water volume, the first drain will reduce your 130 cya to about 97. The next drain will take it to about 73 and the next to 55. Be sure to run the pump for a couple hours after each refill to mix up the old pool water with the new fresh refill.

You may still find yourself using those 3inch tabs at some point. So keep them handy for when you go on vacation and when you may need to add cya next season. Search the forum for proper storage tips. They will also reduce your pH with use. You reported a 7.2 pH reading correct? The pH test with your FC so high will be artificially higher than actual. To be safe, you may want to retest the pH by diluting it down to a 25% sample. Take a measuring cup and fill 3/4 cup with distiller water and 1/4 cup pool water for a full cup of test sample. Stir and then test the pH. If it reads less than before, your gonna want add some (20 Mule Team) Borax to raise the pH back into proper range.

[mjsboone]

7.4 PH last night. I will start this drain/fill process this evening. Off to a tennis tournament!

Thanks for your continued support and quidance. Much appreciated.

[Watermom]

You don't have to drain ....... lots of people just live with the high CYA and just run higher chlorine levels to compensate for it. That works, too. At this point in the summer, you might just want to leave it. Some pools lose a lot of CYA over the winter. You may just want to wait and see where your CYA is in the spring when you open and do some partial drains at that time if it is still high.

http://pool9.net/cl-cya/

I am also a little concerned that you may not be doing the CC test correctly. It is pretty unusual to get that kind of a result. Can you explain your steps that you are following to do the FC and CC test so we can verify that you are doing it properly?

How does your water look?

How consistently are you adding the bleach each night to keep the pool at shock level? It has to be done consistently. Doing it every few days isn't gonna work.

[Big Splash]

Agreed, draining isn't the only option.

[mjsboone]

Back home. Pouring down rain here.

I have tested again. Using the 10ml. sample I added 1 scoop powderand it turned really pink then added37 drops of 871 until clear, multiplied number of drops by 0.5 which equaled 18.5. I then added 5 drops of 003 and sample turned light pink. I then added 4 drops of 871 and it became clear. Multiplied 4x0.5 =2

Last added bleach Weds. night. 5 jugs. Then got scared...I have bleach to go in pool if I need to do that. It just seemed like everything was way out of wack. Water is clear.