TM 9-2320-209-10-1 4-10. OPERATION OF WATER TANK TRUCKS. a. General. Water tank trucks covered in this manual are equipped with a 400-gallon front tank and a 600-gallon rear tank for a total payload capacity of 1,000 gallons when operating on smooth roads. Payload capacity for off-the-road travel is 400-gallons in rear compartment. CAUTION Sanitary precautions must be observed at all times, when handling water and equipment, to keep water clean. At freezing temperatures, delivery pump must be run 60 seconds, with delivery line gate valves open, to drain manifold pipes and delivery pump dry. Water in system could freeze up and cause damage to components. 4-156