I'm curious to know how stable the blend of elements in tap water is. Do you have any data around this?

I once used an inexpensive electrical TDS meter (total dissolved solids) to track the amount of non-organic solids in water both before and after filtering over time. My goal was to determine the rate at which to replace the filter, and it turned out the manufacturer's recommendation was perfect. However I did notice that the unfiltered water's measurement fluctuated a lot over time. Could that pose a challenge in your scenario?

Thanks for a great read, btw.