I just treated my spa for the first time. I had never treated it before so I was expecting the worst. Ahhhsome was a gel, which surprised me. I placed three teaspoons in my spa while it was running full bubbles and water at perfect levels. It bubbled a lot and I got some bubbles that were lined with yellow color but no junk out of the pipes. I actually ran the spa for over an hour scooping out bubbles as I went. No gunk, just some yellow coloring at spots. I was really surprised. I drained the spa, wiped down the sides of it, filled it back up, and ran it for an hour before draining again. I filled it one last time and adjusted the chemicals. I was actually surprised that over this many years the spa was in such pristine shape. During the cleaning process, I had removed the filters and just had them floating in the spa as well.
Maybe I am just lucky, or maybe I keep it always very clean. Maybe the bromine kept it nice, or maybe I just loosened the badness and it will come pouring out later. Who knows. Either way, I am in it tonight and going to enjoy a glass of wine.