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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Membrane Output Calculation Example
What is the expected GPD from a 90 GPD System at 40 psi pressure and
60°F water temperature?
PCF = 40 ÷ 60 = 0.666
TCF = 0.754
Expected GPD = 90 × 0.666 × 0.754 = 45.2 GPD ± 20%
45.2 GPD would be the Actual Production Rate
Performance Test
The performance of a RO membrane is measured by its ability to reject salts
(or TDS -Total Dissolved Solids).
Important: Test the quality of the membrane once every 6 months.
Note: This procedure will require the use of the DM -1 TDS Meter.
Procedure:
1. Measure tap water TDS. This is the “IN” setting on the meter. (Call it X)
2. Run the system for 10-15 minutes.
3. Measure RO water TDS directly on the “OUT” setting on the meter.
(Call it Y).
4. Subtract RO water TDS from tap water TDS. (X - Y)
5. Divide this quantity by tap water TDS. (X - Y) ÷ X
6. Rejection = [(X - Y) ÷ X ] ×100
Rejection of the RO Membrane Calculation Example
1. Tap water TDS = 150 ppm (X)
2. RO water TDS = 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 TDS Rejection = 95.3 %: Rejection rates less than 95% may
indicate that the membrane should be replaced.
