TM 10-6640-215-13 2-8. OPERATING PROCEDURES -continued. (l) Close and latch UTILITIES box access door. (2)   Operate the Water System Using Water Supply Tank As Source. NOTE Keep water tank level at least 1/4 full to ensure fail-free operation of water system. Pump water pressure switch is set to turn the water pump on when pressure drops to 10 psi and to turn the pump off when pressure reaches 20 psi. (a)   In mechanical room, position the water system valves as follows: 1 Filter input valves (2) - CLOSED 2 Pump suction or tank - OPEN to Tank Fill fill directional flow valve (Closed to Pump Suction) 3 Tank fill or water system - OPEN to Water System directional flow valve 4 Water tank drain valve - CLOSED 5 Water system drain - CLOSED valve and petcocks (3) 6 Pump suction valve from tank - OPEN 7 Main water valve from pump - OPEN (b)   Place  the  pump  switch  at  the  pump  controller  to  ON.    Pump  should  run  until  pressure  reaches  cutoff point. (c)   Open  the  sink  faucet  to  purge  air  from  the  system.    Pump  will  start  when  water  pressure  drops  to  the starting point. (d)   When a solid stream of water is flowing from the faucet, close faucet and check system for leaks. (3)   Operate the Water System Using an Outside Pressurized Source. (a)   Unlatch and open UTILITIES box access door. (b)   Connect garden hose adapter to water system connector. (c)   Attach 50-foot (15.25 m) garden hose to adapter. (d)   Position water inlet/outlet selection valve to the IN position. 2-51