Many FD's lead off their fire attack using water from the on-board tank.  Once a permanent water supply is established, make sure that one of the first things you do is to refill the on-board tank.  Leave the tank fill valve cracked open to assure that the tank is totally full and to dispense heat if hose lines are turned off and no other water is flowing.  This will prevent the pump from heating up and causing damage to the pump.