How much CYA should I buy?

jjwalker

Silver Supporter
Aug 23, 2012
198
S. Louisiana
#1
So when I finish my build and start filling...in a few weeks...how much should I buy, assuming pool math is suggesting 80oz to get to 40?

I can buy a 7lb or jump to 25lb...7lb will take care of the fill, but am I going to need a 25lb tub? how much will I need to add say over a year?
 

mfk0213

Gold Supporter
Apr 25, 2016
51
TX
#2
Once you add the CYA, you won't need to add any more except to "top it off" because of splash out and backwash losses, etc. 25lbs will probably last you several years, unless you plan on draining and filling your pool up every season, etc. You can always buy a couple of stabilized chlorine tabs to top off your CYA, as well. I'd say go with the 7lbs, or maybe if you can find a 10 (I got a 10lb bucket at Leslie's back in the day). It'll always be available, as I believe it's a product from industrial waste.

As far as how much you need, you can do the calculation this way. You said you need 7lbs for your pool. So, if you have 3 month swimming season, let's say you backwash weekly ~ 200 gallons. And lose another ~50 gallons to splashout, so 250 gallons per week for 12 weeks = 3000 gallons. The amount of CYA you'll need is 3000/15000 * 7 ~ 1.5 lbs per year. A 25 lb supply would last you about 10-12 years, if you don't drain and fill!

Good luck!

Take care,
Mo
 

mac4lyfe

LifeTime Supporter
Jun 8, 2007
212
Houston, Texas
#4
JJWalker - I would probably start off at CYA 30ppm and see how that works. The recommendation for vinyl pools is 30 - 50 ppm. I'm in Houston, which is similar to your location and I kept my CYA on the lower range so that my FC was lower as well. I didn't see a significant difference in CL burn off by the sun. but your results may vary. maybe try at 30 then see how long it takes to burn off, then try 40 ppm a few weeks later and see how long it takes then. A lower CYA means a lower shock level which means less bleach. My bather load was more than the sun, so it worked better for me to keep cya lower.
 

mfk0213

Gold Supporter
Apr 25, 2016
51
TX
#7
I'm actually considering using it again. I updated the previous post to eliminate confusion.

Good luck with your new pool - it is an exciting journey. If you follow the advice of the senior folks on here, you will undoubtedly have a much easier time thank I did!

Take care,
Mo