What to do next?

[thewayne]

I just opened the pull and got the water level up. My numbers are as follows:

FC 0
CC 0
TC 0
pH 7.8
Alk 290
Cal 150
Cya 0

My pool is a 20,000 gal vinyl ig. And the water is green.

I know i need to shock it but how high do i need to bring the chlorine up?
And what about the cya and Alk?


Thanks

[thewayne]

OK, my memory is coming back now. I haven't thought pool since I closed that thing last year.

According to the cya best guess chart I need 10ppm to shock since I have 0 cya.

So should I shock to 10 first to kill the algae then bring the cya up tp 40 - 50?

And then do alkalinity?

Or should I do Alk first?

[chem geek]

If I were you, I'd use Dichlor to simultaneously add both CYA and FC since adding FC first would get destroyed by the sun very, very quickly. You don't have to get up to the full CYA level, however, as you will need less FC to kill the chlorine if you just get the CYA to 10-20 ppm which should be enough to keep it from getting destroyed too quickly by the sun. You can then raise the FC to the shock level in Ben's table.

Since you have a vinyl liner pool, be very careful about adding the chlorine. Add it very slowly over a return with the pump running. In the case of the Dichlor, you might want to premix it in a bucket first.

You can deal with the TA after your algae bloom has cleared and you've adjusted your CYA and FC to their final levels. Use the TA lowering procedure of lowering the pH to around 7.0 - 7.2, aerating, adding acid (carefully and slowly, again over a return) to keep the pH low. When the TA gets to where you want it, stop adding the acid and keep aerating. The pH will then rise and stop aerating when you get to 7.5 or wherever you want your pH to be.

Richard