TM 9-2320-209-10-1 b. Water Tank Trucks Controls and Indicators. 1. Gravity delivery line suction valve. 3. 400 gallon compartment valve lever Is turned left to let water flow through and 600 gallon compartment valve gravity delivery line. lever. Are pulled back to open dis- 2. Pump delivery line discharge valve. charge valves which control flow of Is turned left to let water flow through water. pump delivery line. 4. Water level gage. Is dipped into tank sections to measure water level. 4-13