Bringing back an old thread, because I just had this exact same issue. After following the directions precisely, my water is milky white, and there is a layer of white "powdery dust on the steps and floor that keeps coming back every time I brush. I spoke with the manufacturer, who was very friendly, knowledgable, and helpful. They are indicating this is a result of the product extracting calcium staining from the plaster. They indicate the powder is Calcium Carbonate.
Now the bad news. They said to run the filter and in a day or two it would clear. I did this and there is no difference. I called back. They said the calcium carbonate may be small enough that it is pass through the sand filter, and therefore not being removed. Uh-oh!
I am experimenting with some things I discussed with the rep. I am lower the RPM on the pump, I only have the floor drain open, and am brushing the powdery stuff towards the deep end (where the floor drain resides). The rep said I may need to add something like DE to create a finer particle filter layer in the sand filter, but I hate to do this just to fix this issue that the product caused.
Open to any knowledge or advice.