if your container water level is above the pump it will gravity feed into the pump, if its lower then the pump will have to pull it through
i used an old wheely bin with the 6ft of hose connected to the bottom, when the bin was full i would lower the hose below the water level and allow it to spurt out, then stick my finger over it, then connect it to the machine...... sound complicated but it was a 5 second job.
i never liked to just stick my hose over the top of the bin and let it dangle into the water