(9) Remove product water hose (14, fig. 2-28) from product water tank and allow hose from
ROWPU to drain on the ground. Leave brine water hose in backwash water tank.
If element cleaning does not start, it maybe necessary to loosen draincock on
backwash pump to purge air. Close draincock when pump is primed.
(10) Within a few seconds, BRINE FLOW indicator (16, fig. 2-4) should show a flow of 16 gpm or
If pH of water circulating through R.O. elements drops below 3.5, element
membranes may be damaged.
(11) After 5 minutes, check pH (para. 2-32) of water discharging back into brine tank; it should be
near, but not below, 3.5. If it isnt, add another pound of citric acid and stir until all granules are dissolved.
If in the past, when using the same source water, brine has been very alkaline,
then more citric acid may be added; however, never let pH of the water
circulation through R.O. elements drop below 3.5.
(12) Continue checking pH and adding 1 lb of citric acid at 5 minute intervals until pH of water is
near, but not below, 3.5.
(13) Allow citric acid solution to circulate for 45 minutes. Periodically check the temperature of the
water discharging back into brine tank; use thermometer in Storage Box No. 2.
Temperature of solution will rise during element cleaning. At no time should it
exceed 120°F. If temperature rises above 120°, stop recirculating citric acid
solution and resume normal operation.
(14) Stop recirculation by pushing the ELEMENT CLEANING switch down to OFF.
(15) Remove VENT VESSELS hose from outlet of the backwash pump and connect BACKWASH
WATER hose to backwash pump outlet.
Drainage lagoon should be located downstream from unit.
(16) Drain citric acid solution into a shallow man-made lagoon a reasonable distance away from
the unit. Close valve at discharge of brine water tank (para. 2-66).
2 - 78