TM 9-2320-209-10-1 g. Operating Water Tank Trucks During Freezing Temperatures. FRAME 1 CAUTION Do not heat water tank with less than 10 inches of water in both front and rear tank sections. The 10 inches of water prevents heat from building up in parts of the tank. Metal expansion due to the heat could cause cracks in seams and welds. 1. Take off padlocks (1) open tank section filler covers (2). 2. Measure water level in each tank section using water level gage (3) for front section and water level gage (4) for rear section. GO TO FRAME 2 4-195