ZIP WATER PURIFIER USER GUIDE
RO MEMBRANE REPLACEMENT
How to tell if the RO membrane needs replacement:
The condition of the membrane is assessed by testing the percent TDS rejection:
Using a TDS meter, compare the TDS of the inlet water to the pure RO water and obtain the percent-
age of TDS rejection. TDS testers are widely available to purchase if you wish to test your own TDS.
% rejection rate = TDS of inlet water –
TDS of pure water x100
TDS of inlet water
Example:
Inlet water TDS = 300ppm; Pure water TDS = 18ppm
300
–
18
x100 +90% rejection rate
300
If rejection goes below 70% the membrane life has come to an end.
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