There are lots of things you can measure when testing the quality of your water, for sanitation and comfort. Many of which aren't specifically designed for float tanks. This is kind of an open secret in the industry, but most things simply aren't accurate because of the incredibly high salinity of float tank solution. And pH seems to be one of them. This can cause float center owners major headaches as it's often one of the first things that health departments/regulators will want to measure when they come and inspect your place (if they do at all). 

Graham and Ashkahn try to break down this mystery of float water and try to break down some theories as to why it might be that float tank water might not have accurate pH readings, regardless of how you measure it.