CYA concentration in trichlor pucks

Do any of the pucks have lower CYA percentage or are they all the same?

Most pucks are made of trichlor (trichloro-isocyanuric acid AKA any of a dozen or so other tnames); all of those have virtually identical CYA levels

EXCEPT for some of the "dual-action" or "triple-action" pucks that have been diluted with various low cost chemicals: those are lower in BOTH cyanuric acid AND chlorine; AVOID THEM.

Arch / HTH and PPG make a variety of pucks, tablets, and lozenges that contain mostly calcium hypochlorite. These are more common in the institutional market, but occasionally are seen on the retail market. These contain no stabilizer.

Thanks, that is what I figured. Do you know what the ratio of chlorine to CYA is in the pucks?

Each pound of trichlor or dichlor used will add approximately 1/2 pound of CYA to your pool, considered from the point of view of bulk chemical.

As active percentages, dichlor is 55% available chlorine and 50% CYA; trichlor is 90% available chlorine and 60% CYA. (I know those don't add to 100% -- it has to do with the way "available chlorine" and ppm chlorine in water is defined.)

As ppm FC added to your pool, for each 1 ppm of FC, trichlor will add 0.6 ppm of CYA; dichlor will add 0.9 ppm of CYA