adjust cya before or after shocking

[Kateyru]

Hi,
I have an inground pool with SWG and vinyl liner. Since I live in Alabama, we don't really close our pool over the winter. We actually were in the pool in March My CYA is 30, and I have a little green algae which I really struggled to get rid of last summer and early fall. Not sure I got it all because it's in there now. My FC is 5, Ph is 7.6, and TA is 80. Should I get CYA to 70 before shocking with bleach to get rid of the algae or should I shock then add CYA?
Thanks so much. The website and forum have been extremely helpful.

[aylad]

Hi Kateyru, and welcome to the forum!!

I would shock with bleach to get rid of the algae, holding it at shock level until you are no longer lose any chlorine overnight (measuring it after sundown and again in the morning before the sun is on the pool). Once the algae is gone, then raise your CYA.

[BigDave]

I would go after the algae first and then raise the CYA after you're done, it should take less bleach to get to your shock level with a lower CYA. If dichlor shock is cheap in your area, you may consider using it to start your algae battle - it will add CYA as well as chlorine. Be sure to watch your CYA and pH if you do.

[Kateyru]

Will do, thanks!

[Kateyru]

Okay, I added dichlor last night. I tested ph this morning and it is way up...at least 8.2 (as high as my kit goes). I thought dichlor would lower the ph??? Should I add muriatic acid this morning?
Thanks.

[Watermom]

What is your chlorine level? If you test pH when they chlorine level is high, you can get false pH readings.

[Kateyru]

at least 10, it doesn't look much darker than that