TM 55-1930-209-14&P-19 Table 2-4.  Preventive Maintenance Checks and Services for Seawater System (Continued) B - Before D - Daily Q -  Quarterly D - During W - Weekly S -  Semiannually A - After M - Monthly A -  Annually INTERVAL ITEM PROCEDURES EQUIPMENT ITEM TO BE CHECK FOR AND HAVE IS NOT READY/ NO. INSPECTED REPAIRED OR ADJUSTED AVAILABLE IF B   D   A   D  W  M   Q   S   A AS NECESSARY * Liquid Level e.  Flush liquid level indicator with drinking Indicator water as follows: 1)  Empty seawater ballast tank 2)  Disconnect 2 pipe unions connecting indicator to tank.  Remove indicator. 3)  Flush indicator by allowing drinking water to flow into top pipe connector and out of bottom pipe connector. 4)  Connect indicator to tank by tighten- ing pipe unions. 5)  Check for leaks and for indication on equipment monitoring system.  Check visual flag indicator when ballast tank is refilled. * f.  If seawater source is high in debris perform BLOWDOWN as follows: CAUTION During seachest blowdown, be sure regulator 2 pressure gauge reads 40 psi.  Reset if necessary by turning adjusting screw. 1)  Prestart * Make sure air compressor is operating.  if not, start up in accordance with air compressor system operation. * Check that compressed air pressure regulator 2 is set to 40 psi as shown on regulator gauge. * Make sure seachest is not in use. 2-16