Table 1. Major Functional Components of the ROWPU System (Refer to Figure 3)
ROWPU System General
The pressure reducing valve ensures that overall
Service Pressure Reducing
general service system pressure is maintained at a
maximum of 60 PSI (4.1 bar).
ROWPU System Raw Water
The cutout valve allows the operator to secure raw water
to the ROWPU system.
ROWPU System Raw Water
The pressure regulator maintains the raw water supply to
the ROWPU system at a constant pressure of 40 PSI
ROWPU System Pressure
The pressure relief valve protects the ROWPU system
by providing pressure relief when raw water pressure
exceeds 50 PSI (3.4 bar).
ROWPU System Media Filter
The media filter uses sand as a substrate to remove
larger particles that would cause clogging of the 20-
micron pre-filter. The substrate in the media filter
requires very infrequent change out due to the ability to
back flush. During back flushing, the media filter is
completely isolated from the rest of the ROWPU
system, while raw water from the general service
system cleans and flushes debris overboard. The media
filter prolongs the service life of the 20-micron filter.
The 20-micron pre-filter removes all particulate in the raw
water not removed by the media filter down to particles
20 microns in size. This filter serves to prolong the
service life of the 5-micron pre-filter.
The 5-micron pre-filter removes all particulate in the raw
water not removed by the 20-micron pre-filter down to
particles 5 microns in size. This filter serves to prolong
the service life of the reverse osmosis membranes.
High Pressure Pumps
The high pressure pumps provide a source of low
volume, high pressure raw water to the reverse osmosis
membranes. The high pressure pumps are rated to
deliver 4 gallons (15.1 liters) of filtered raw water per
minute, at a maximum operating pressure of 900 lb/in
(62 bar). The high pressure pumps provide the fluid
energy necessary to cause the osmosis process to be
reversed in the membranes.
The membranes convert filtered raw water into drinking
water by allowing only water molecules to pass through
its spiraled membrane. The high pressure/low volume
pumps push raw water through the membranes to make
fresh water, and they push the brine out of the
membranes and overboard.