I used to occasionally shock with granules so I guess it's come from that. I think I did one last week while waiting for the test kit and for the feeder to sort itself out. But, maybe my first test was wrong and it was never 250 to start with. It was the first day of using the new test kit. I can't imagine our drinking water/ refill water being that high.
It's the only thing that makes sense.
I'll make sure to use liquid from now on for slam etc.
In the USA the local water suppliers must provide us a chemical analysis of our water. For example, the water we use here in Nevada is from the Colorado River and has a CH of 250 ppm, TA of 130 ppm, and pH of 8.