Watts R4X40-3 - Manual (Page 7)

Prefilter Cartridge - Used to remove smaller suspended solids and trap any particles that may be
generated by the other pretreatment. The cartridge(s) should be replaced when the pressure drop
across the housing increases 5 - 10 psig over the clean cartridge pressure drop.
The effect of suspended solids is measured by the silt density index (SDI) test. An SDI of five
(5) or less is specified by most membrane manufacturers and three (3) or less is recommended.
Iron & Manganese - These foulants should be removed to less than 0.1 ppm. Special media
filters and/or chemical treatment is commonly used.
pH - The pH is often lowered to reduce the scaling potential. If the feed water has zero hardness,
the pH can be raised to eliminate CO2.
Silica: Reported on the analysis as SiO2. Silica forms a coating on membrane surfaces when the
concentration exceeds its solubility. Additionally, the solubility is highly pH and temperature
dependent. Silica fouling can be prevented with chemical injection and/or reduction in recovery.
II. CONTROLS, INDICATORS, and COMPONENTS (see figure 1)
A. On / Off Switch – Turns the unit on and off.
B. Low-pressure indicator – Turns on when low pump inlet pressure is detected.
C. Reject Control Valve - Controls the amount of reject flow.
D. Reject Recycle Control Valve – Controls the amount of recycle flow.
E. Prefilter Outlet Pressure Gauge - Indicate the outlet pressures of the prefilter.
F. Pump Discharge Pressure Gauge - Indicates the membrane feed pressure.
G. Reject Flow Meter - Indicates the reject flow rate in gallons per hour (gph).
H. Product Flow Meter - Indicates the product flow rate in gallons per hour (gph).
I. Prefilter Housing - Contains the RO prefilter.
J. RO Feed Pump - Pressurizes the RO feed water.
K. RO Membrane Housing(s) - Contains the RO membrane(s).
L. Water Quality Meter – Indicates the quality of the feed and product water in parts per
million of total dissolved solids (PPM – TDS).
M. Feed Water Inlet.