Pool is filling! Need help checking my math:)


Active member
Aug 17, 2010
Champaign, IL Area
I've been silenting learning here over the past month while waiting for our pool to be installed. I grew up with a pool but I'm definitely a lot rusty on all of this:) I have my TF100 kit in-hand but I haven't tested anything yet--can't wait, I was a chem major when I started out in college;)--and read Pool School...I'm sure I'll still be referring back to it often though.

I know I need to add chlorine (to get myself to 3-4ppm) and CYA (to get myself to 30 ppm for now) to start. I used the pool calculator and came up with the following for my 11,700 gallon round 21', 54" depth AG pool:

47 oz/wt or 49 oz/vol of CYA/Stabilizer - I have 2lbs (32 oz) of Stabilizer that came with the pool startup kit, so I'll need to go out and get another pound (should I go ahead and get any more or is it not necessary...we'll probably have the pool open for another 1.5 months). I know once you add it, it's not really going anywhere unless there's significant water replacement, but I didn't know if I should shoot for a number higher than 30ppm at this point (but I guess that will depend on how fast my chlorine is dissipating once I get things up and going).

97 oz of 6% bleach or 8.6 oz/wt of 73% cal-hypo - I have 1 lb of 73% cal-hypo that came with the startup kit. Is there any reason not to use this? If I can use it, how should I add this to the pool since it's a granular substance? (I'm sure I can look this up in Pool School as well but I need to run off to get my child who is waking from his nap soon.) Since I only have 1 lb of cal-hypo, I'll still need to make a run to the store for bleach (probably Aldi's or WallyWorld :) ).

Does my math compute here? Am I missing anything critical at this point? I know I may need to adjust my PH after I get those things in there when I start testing and testing and testing :-D but is there anything else?


Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
Houston, Texas
Since you have your test kit go ahead and practice on your fill water. CH is not as important as it is to a plaster pool, but too much can still cause a vinyl lined pool to develop scale. If your fill water is very high in CH then I would not use the cal-hypo but other wise it should be fine.

Stick with 30 ppm of CYA to start. It is much easier to add if needed than to drain to remove excess.

By the way, 2 hp is a heck of a lot of pump for a 21' pool. I have a 1.5 and with a clean filter it is like a lazy river ride when the pump is on!


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Welcome to the forum!! :lol:
Does my math compute here? Am I missing anything critical at this point?
Math looks right. The best thing you could do is post test results from your fill water.

30 is fine for CYA rest of this season.

Hang on to the Cal Hypo for now until you post your test results.


Active member
Aug 17, 2010
Champaign, IL Area
Ok, I tested my fill water and here's what I came up with. I don't have T/A listed because I got to 30 drops of R0009 on two separate tries and figured I have to be doing something wrong, so I stopped. Not sure what my error is. I'm confident about my other numbers.

FC 1.5
CC 0
TC 1.5
pH 8
CH 70

I'm assuming that since I'll be adding CYA, I'll want to wait on doing anything about my pH.

So, since my CH is within an acceptable range, could I use up my 1 lb packet of cal-hypo and then switch to just bleach?



LifeTime Supporter
Feb 26, 2010
Guam, USA
Congrats on the new pool! I would go ahead and use the cal-hypo, since you've got it anyways. Adding CYA usually does not affect the Ph much, so you'll need some muriatic acid to lower it. Just remember, once you add CYA, it will take about a week for it to show up on the test. To save reagent, wait about a week to test, but when adding chlorine, calculate your chlorine levels based upon your CYA target level until you do the test.

Enjoy your new pool :)
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