Use of chlorine pucks


Active member
Oct 11, 2013
Jackson, Mississippi
I have read on here about caution against using tri-chlor pucks because of the CYA. I like the idea of the convenience and price and am not too concerned about the CYA because I can check it with my Taylor test kit. Are there any other downsides? I need about one puck per day for my 30,000 gallon vinyl pool. How long would it take to raise the CYA by 10 ppm?

Brett S

Well-known member
Mar 15, 2019
One 8oz trichlor puck in 30,000 gallons will raise your FC level by 1.8ppm and raise your CYA level by 1.1ppm, so your CYA level will go up by 10ppm about every 9 days at that rate.


Bronze Supporter
Jul 17, 2019
Prosper, TX (DFW)
Every 1lb of Tri-chlor in a 30k pool will raise FC by 3.7 and CYA by 2.2.

Assuming 1lb every other day, you are raising your CYA by just under 10 a week. As long as you can manage that, it is fine, but its a slippery slope when your CYA gets 50+ because you need more FC for it to be effective and in turn add more CYA.


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

We have no problem with people using pucks, as long as they are aware of the issue with high CYA... Many people just monitor their CYA level and then drain and refill some pool water to keep the CYA in range.

The other problem with using tabs is that most people do not keep their FC high enough to prevent algae.. To compensate for this they dump in two bags of shock once a week.. I personally don't like the public pool smell.


Jim R.


TFP Expert
LifeTime Supporter
Jun 12, 2009
NW Ohio
wish theyd just make pucks with less cya...
That's about akin to saying "I wish they'd just make water with less hydrogen". CYA is part of the chemical makeup of trichlor, you can't just take a little out.

As to the original question: they are also quite acidic so make sure you carefully monitor your pH and TA levels. Of course, you can't just add 1 puck a day because as the CYA rises 10 ppm per week you need to also raise your FC by about half a ppm per week. So you have to add some extra. Which also means more CYA. And then about once a month you will want to exchange about 30% of your water to keep your CYA in check. I can't imagine how dumping 10,000 gallons of water a month would be convenient. I also can't imagine how it is that much more convenient handling a puck as pouring half a gallon of liquid chlorine. Those things really leave a chloramine scent on the skin.

And I sure hope you considered the water exchange in to your price calculations. Pucks already aren't much cheaper than liquid chlorine when you calculate amount of chlorine. Throw in baking soda additions and thousands of gallons of water a month and things don't look very rosy for pucks. Not that it can't be done, but the reasoning seems to come up pretty darn short of reality. At the end of the day one has to wonder why an SWG isn't in consideration as it comes with all the convenience (and more!) and none of the downside.