At this point raw tapwater reading is 15 ppm; post RO reading is 0 ppm; and obviously if post RO is 0 then the rest....post MaxCap DI cartridge (stage 4), and post SilicaBuster cartridge (aka finished product water)....are also presently at 0 ppm.
The advantage to having the 4 readings is one can determine the status of the RO membranes [(Tapwater ppm - post RO ppm) / tapwater ppm] x 100 = membrane rejection rate %.
And.....one can determine the status of the first DI cartridge (the MaxCap cartridge). When the post MaxCap DI cartridge (stage 4) reading is 75% of the post RO reading, it's time to replace the cartridge. The indicator for replacing the second DI cartridge (the SilicaBuster) is simply a rise to 1 ppm on the last TDS reading. (The product reading).
Cheers,
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Mark.
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