Most commonly, deposits on your spa shell are due to calcium scaling. In mild forms this appears as a sort of “dust” on your spa shell. As it gets more severe, this scaling becomes very hard and will feel like sandpaper.
Realize that this scaling is not just on your spa shell. It will be everywhere under water in your spa, including inside your jets (hence they stop spinning), in your filter(s) & plumbing (restricting water flow), and in your pump. This scaling is more than an annoyance. It can cause serious problems in your hot tub.
Calcium scaling is ALWAYS due to high spa water pH. If your pH is above 8.0, your spa is at risk of Calcium scaling. It’s true spa water with higher levels of Calcium, particularly when above 250 ppm, is more likely to experience Calcium scaling however, it still will not occur if your pH is in the proper range of 7.2 – 7.6.
