** ***
b. Use of water in training. Water may be used (instead of fuel) for elementary practice firing. Ignition cylinders are * * * piece, and lubricated ([Par. 49]). Use of water, however, should always be supplemented by firing ignited fuel because water does not give a correct impression of stream and flame characteristics.
** ***
17. CONNECTING TANK GROUP AND GUN GROUP.
** ***
a. Place the new * * * to 2 minutes. Slight pressure sometimes builds up in the fuel tanks, even though the pressure-tank valve has not been opened, and causes some overflow of fuel when the coupling plug is removed. This pressure may be relieved by—
(1) Standing the tank group upright.
(2) Slightly opening filling plug on top of fuel tanks to bleed the pressure.
(3) Closing the opening at filling plug and tightening it with wrench.
** ***