My 1st readings, what type chlorine to add?

May 26, 2008
Not using my Frog and going to BBB but I'm still confused about the different kinds of chlorine between tabs, shock and bleach. I have on-hand some 3" chlorine tabs from last year and 2 years ago, some shock and a big bottle of bleach.
My pool opened beautifully clear last week and I've added bleach once. My readings are:
FC 3.5
CC 0
TC 3.5
PH 7.5
CH 290
T/A 90 (Is this OK?)
CYA 35

From what I read here, if I use the shock, it will raise the CYA. That's a good thing in this case, right? And, the tabs (cal hypo) will raise the CH but not the CYA, right? I'm running out of bleach so I'd like to use the shock and the tabs on a limited basis if I can. The tabs are individually wrapped. Have those lost significant strength?
Fought algae all last year and trying to avoid that.
Thank you.


LifeTime Supporter
TFP Expert
In The Industry
May 20, 2007
SWSuburban Chicago, IL
Hello and Welcome to TFP!

I just want to clarify - Shock is something you do, it is not a 'product' despite what the pool stealers will tell you. Yes, most forms of 'shock' as they call it contain CYA. Liquid chlorine, a.k.a. bleach, does not. Bleach is by far the least expensive method of sanitizing your water. Hands down.

Your numbers look good. IF you are going to use up the pucks or any source of non-liquid chlorine, keep a careful eye on your CYA and I would recommend not going above 50-60.

Some "shock" as they call it does not contain chlorine at all. So watch your ingredients. Please read the articles BBB for beginners and the ABCs of pool chemistry. There are others, that i'm forgetting right now, but if you have any questions at all, post them here!

Glad to hear your Frog decision.... :goodjob:
The most common forms of shock (liquid and cal hypo) do NOT add CYA. The only one that does is dichlor.
Stop thinking in terms of chlorine and shock and start thinking in terms of stabilzied chlorine which adds CYA (trichlor and dichlor) and unstabilized chlorine which doesn't (liquid chlorine or bleach, calcium hypochlorite or cal hypo, and lithium hypochlorite). Read the ingredient labels and you will know whether the product will add CYA!
Also, as mentioned above, there are non chlorine 'shocks' too. These are potassium monopersulfate (MPS). They really are not the best choice for an outdoor pool.
May 26, 2008
Thank you both for the concise answers..sometimes I have trouble seeing the trees for the forest! Also bookmarked the CYA/Chlorine chart, just what I need. Thanks again.