TM 10-6640-238-13 2-49 NOTE In Mod Lab B ensure input valve prefilter is closed. (g) In mechanical room, position water system valves as follows: 1 Input valve prefilter - OPEN 2 Input valve postfilter - OPEN 3 Pump suction or tank fill directional flow valve - OPEN to Tank Fill 4 Water flow direction valve - OPEN to Tank Fill 5 Water tank drain valve - CLOSED 6 Water system drain valve - CLOSED 7 Pump suction valve from water tank bottom - CLOSED 8 Filter backwash valve - CLOSED 9 Water return drain valve - CLOSED 10 Water pump drain valve - CLOSED 11 Pump suction drain valve - CLOSED (h) Slowly turn on water supply at source. (i) Continue to fill water tank until water flows out from overflow drain under trailer. (j) Turn off water supply at source. (2) Operate 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 water pump on when pressure drops to 10 psi and to turn pump off when pressure reaches 20 psi. (a)     In laboratory, position water system valves as follows: 1 All water supply valves located above countertop. - CLOSED 2 Water supply drain valve under sink. - CLOSED 3 Water supply drain valve to hot water. - CLOSED (b) In mechanical room, position water system valves as follows: 1 Input valve prefilter - CLOSED 2 Input valve postfilter - CLOSED 3 Pump suction or tank fill directional flow valve - CLOSED to Pump Suction 4 Water flow directional valve - CLOSED to Water System 5 Water tank drain valve - CLOSED 6 Water system drain valve - CLOSED 7 Water return drain valve - CLOSED 8 Water pump drain valve - CLOSED