SpectraPure
®
SpectraPure
®
Inc.
480.894.5437 Call us toll-free 1.800.685.2783
2167 East Fifth St, Tempe, Arizona 85281
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TESTING THE QUALITY OF THE MEMBRANE
The performance of a RO membrane is measured in terms of its rejection characteristics. Note:Test the quality of the
membrane once every 6 months.
Method 1: Using a test kit
The rejection of the membrane is measured using the following procedure:
1. Turn the right-angled ball valve on the top of the pressure tank to the OFF position. Flip the faucet lever into the
UP position.
2. Measure tap water conductivity* (Call it X).
3. Run the system for 30 minutes.
4. Rinse test instrument cell 2-3 times with RO water.
5. Measure RO water conductivity* (Call it Y).
6. Subtract RO water conductivity* from tap water conductivity* (X - Y) .
7. Divide this quantity by tap water conductivity* (X - Y) ¸ X .
8. Rejection = [(X - Y) ¸X ] ´ 100 .
9. Put the faucet lever back to the DOWN position and then turn the right-angled ball valve to the ON position.
Example: Calculation of Rejection of the RO Membrane.
1. Tap water hardness = 150 ppm (X).
2. RO water hardness = 7 ppm (Y).
3. X - Y = 143 ppm.
4. (X - Y) ÷ X = 143 ÷ 150 = 0.953
5. Rejection = [ ( X - Y) ÷ X ] ×100 = 0.953 ×100 = 95.3
Membrane Hardness Rejection = 95.3 %
*Depending on your tap water chemistry, the rejection characteristics of the membrane may vary significantly.
TIPS FOR GOOD MEMBRANE LIFE
Following tips will ensure a good membrane life:
1. Replacement of 0.5 micron MicroTec™ sediment filter once every 6 months OR when the pressure indicated by
the pressure gauge drops by 15-20% (whatever happens first). This will prevent membrane fouling due to silt or
sediment depositing on the membrane.
2. Replacement of 0.5 micron carbon block filter at least once every 6 months OR when the pressure indicated by the
pressure gauge drops 15-20% (whatever happens first) OR when chlorine breakthrough occurs*. This will ensure
good membrane life and prevent membrane from chlorine damage.
3. Membrane should not be operated at lower than 4:1 waste water to product water ratios. If you have a lower ratio,
change the length of the flow restrictor to adjust to at least 4:1.
4. Running reverse osmosis systems on softened feed water reduces the chances of membrane fouling.
* Method to check for chlorine breakthrough: Detection of chlorine levels > 0.1 ppm in brine (1/4” yellow waste water
line). USE PART #: TK-CL-10-KIT (Total Chlorine Test Kit).
