So last season, I needed to add a touch of CYA, and I did so by very, very slowly adding it to one of the skimmers. Imagine my surprise when a minute or so later I started seeing little white granules coming out from the return. I thought that certainly was indicating a rip in one or more of the cartridges. They aren't terribly expensive so I bought a new set to install this season.
We opened yesterday, I installed the brand new cartridges, and sure enough, I needed to increase CYA just a touch. So again, I added it very slowly to the skimmer, and again, little white granules start coming out the return.
In neither case was the volume of granules equal to what I put in. Just a few here and there, but clearly visible and noticeable.
How is that possible?
It's a Hayward Swimclear C4030